diff --git a/vnpy/app/cta_strategy/converter.py b/vnpy/app/cta_strategy/converter.py
new file mode 100644
index 00000000..67bbada2
--- /dev/null
+++ b/vnpy/app/cta_strategy/converter.py
@@ -0,0 +1,297 @@
+""""""
+from copy import copy
+from functools import lru_cache
+
+from vnpy.trader.engine import MainEngine
+from vnpy.trader.object import (
+    ContractData,
+    OrderData,
+    TradeData,
+    PositionData,
+    OrderRequest
+)
+from vnpy.trader.constant import (Direction, Offset, Exchange)
+
+
+class OffsetConverter:
+    """"""
+
+    def __init__(self, main_engine: MainEngine):
+        """"""
+        self.main_engine = main_engine
+        self.holdings = {}
+
+    def update_position(self, position: PositionData):
+        """"""
+        if not self.is_convert_required(position.vt_symbol):
+            return
+
+        holding = self.get_position_holding(position.vt_symbol)
+        holding.update_position(position)
+
+    def update_trade(self, trade: TradeData):
+        """"""
+        if not self.is_convert_required(trade.vt_symbol):
+            return
+
+        holding = self.get_position_holding(trade.vt_symbol)
+        holding.update_trade(trade)
+
+    def update_order(self, order: OrderData):
+        """"""
+        if not self.is_convert_required(order.vt_symbol):
+            return
+
+        holding = self.get_position_holding(order.vt_symbol)
+        holding.update_order(order)
+
+    def update_order_request(self, req: OrderRequest):
+        """"""
+        if not self.is_convert_required(req.vt_symbol):
+            return
+
+        holding = self.get_position_holding(req.vt_symbol)
+        holding.update_order_request(req)
+
+    def get_position_holding(self, vt_symbol: str):
+        """"""
+        holding = self.holdings.get(vt_symbol, None)
+        if not holding:
+            contract = self.main_engine.get_contract(vt_symbol)
+            holding = PositionHolding(contract)
+            self.holdings[vt_symbol] = holding
+        return holding
+
+    def convert_order_request(self, req: OrderRequest, lock: bool):
+        """"""
+        if not self.is_convert_required(req.vt_symbol):
+            return [req]
+
+        holding = self.get_position_holding(req.vt_symbol)
+
+        if lock:
+            return holding.convert_order_request_lock(req)
+        elif req.exchange == Exchange.SHFE:
+            return holding.convert_order_request_shfe(req)
+        else:
+            return [req]
+
+    @lru_cache
+    def is_convert_required(self, vt_symbol: str):
+        """
+        Check if the contract needs offset convert.
+        """
+        contract = self.main_engine.get(vt_symbol)
+
+        # Only contracts with long-short position mode requires convert
+        if not contract.net_position:
+            return True
+        else:
+            return False
+
+
+class PositionHolding:
+    """"""
+
+    def __init__(self, contract: ContractData):
+        """"""
+        self.vt_symbol = contract.vt_symbol
+        self.exchange = contract.exchange
+
+        self.active_orders = {}
+
+        self.long_pos = 0
+        self.long_yd = 0
+        self.long_td = 0
+
+        self.short_pos = 0
+        self.short_yd = 0
+        self.short_td = 0
+
+        self.long_pos_frozen = 0
+        self.long_yd_frozen = 0
+        self.long_td_frozen = 0
+
+        self.short_pos_frozen = 0
+        self.short_yd_frozen = 0
+        self.short_td_frozen = 0
+
+    def update_position(self, position: PositionData):
+        """"""
+        if position.direction == Direction.LONG:
+            self.long_pos = position.volume
+            self.long_yd = position.yd_volume
+            self.long_td = self.long_pos - self.long_yd
+        else:
+            self.short_pos = position.volume
+            self.short_yd = position.yd_volume
+            self.short_td = self.short_pos - self.short_yd
+
+    def update_order(self, order: OrderData):
+        """"""
+        if order.is_active():
+            self.active_orders[order.vt_orderid] = order
+        else:
+            if order.vt_orderid in self.active_orders:
+                self.active_orders.pop(order.vt_orderid)
+
+        self.calculate_frozen()
+
+    def update_order_request(self, req: OrderRequest, vt_orderid: str):
+        """"""
+        gateway_name, orderid = vt_orderid.split(".")
+        order = req.create_order_data(orderid, gateway_name)
+        self.update_order(order)
+
+    def update_trade(self, trade: TradeData):
+        """"""
+        if trade.direction == Direction.LONG:
+            if trade.offset == Offset.OPEN:
+                self.long_td += trade.volume
+            elif trade.offset == Offset.CLOSETODAY:
+                self.short_td -= trade.volume
+            elif trade.offset == Offset.CLOSEYESTERDAY:
+                self.short_yd -= trade.volume
+            elif trade.offset == Offset.CLOSE:
+                if trade.exchange == Exchange.SHFE:
+                    self.short_yd -= trade.volume
+                else:
+                    self.short_td -= trade.volume
+
+                    if self.short_td < 0:
+                        self.short_yd += self.short_td
+                        self.short_td = 0
+        else:
+            if trade.offset == Offset.OPEN:
+                self.short_td += trade.volume
+            elif trade.offset == Offset.CLOSETODAY:
+                self.long_td -= trade.volume
+            elif trade.offset == Offset.CLOSEYESTERDAY:
+                self.long_yd -= trade.volume
+            elif trade.offset == Offset.CLOSE:
+                if trade.exchange == Exchange.SHFE:
+                    self.long_yd -= trade.volume
+                else:
+                    self.long_td -= trade.volume
+
+                    if self.long_td < 0:
+                        self.long_yd += self.long_td
+                        self.long_td = 0
+
+        self.long_pos = self.long_td + self.long_yd
+        self.short_pos = self.short_td + self.short_yd
+
+    def calculate_frozen(self):
+        """"""
+        self.long_pos_frozen = 0
+        self.long_yd_frozen = 0
+        self.long_td_frozen = 0
+
+        self.short_pos_frozen = 0
+        self.short_yd_frozen = 0
+        self.short_td_frozen = 0
+
+        for order in self.active_orders.values():
+            # Ignore position open orders
+            if order.offset == Offset.OPEN:
+                continue
+
+            frozen = order.volume - order.traded
+
+            if order.direction == Direction.LONG:
+                if order.offset == Offset.CLOSETODAY:
+                    self.short_td_frozen += frozen
+                elif order.offset == Offset.CLOSEYESTERDAY:
+                    self.short_yd_frozen += frozen
+                elif order.offset == Offset.CLOSE:
+                    self.short_td_frozen += frozen
+
+                    if self.short_td_frozen > self.short_td:
+                        self.short_yd_frozen += (self.short_td_frozen
+                                                 - self.short_td)
+                        self.short_td_frozen = self.short_td
+            elif order.direction == Direction.SHORT:
+                if order.offset == Offset.CLOSETODAY:
+                    self.long_td_frozen += frozen
+                elif order.offset == Offset.CLOSEYESTERDAY:
+                    self.long_yd_frozen += frozen
+                elif order.offset == Offset.CLOSE:
+                    self.long_td_frozen += frozen
+
+                    if self.long_td_frozen > self.short_td:
+                        self.long_yd_frozen += (self.long_td_frozen
+                                                - self.long_td)
+                        self.long_td_frozen = self.long_td
+
+            self.long_pos_frozen = self.long_td_frozen + self.long_yd_frozen
+            self.short_pos_frozen = self.short_td_frozen + self.short_yd_frozen
+
+    def convert_order_request_shfe(self, req: OrderRequest):
+        """"""
+        if req.offset == Offset.OPEN:
+            return [req]
+
+        if req.direction == Direction.LONG:
+            pos_available = self.short_pos - self.short_pos_frozen
+            td_available = self.short_td - self.short_td_frozen
+        else:
+            pos_available = self.long_pos - self.long_pos_frozen
+            td_available = self.long_td - self.long_td_frozen
+
+        if req.volume > pos_available:
+            return [req]
+        elif req.volume <= td_available:
+            req_td = copy(req)
+            req_td.offset = Offset.CLOSETODAY
+            return [req_td]
+        else:
+            req_list = []
+
+            if td_available > 0:
+                req_td = copy(req)
+                req_td.offset = Offset.CLOSETODAY
+                req_td.volume = td_available
+                req_list.append(req_td)
+
+            req_yd = copy(req)
+            req_yd.offset = Offset.CLOSEYESTERDAY
+            req_yd.volume = req.volume - td_available
+            req_list.append(req_yd)
+
+            return req_list
+
+    def convert_order_request_lock(self, req: OrderRequest):
+        """"""
+        if req.direction == Direction.LONG:
+            td_volume = self.short_td
+            yd_available = self.short_yd - self.short_yd_frozen
+        else:
+            td_volume = self.long_td
+            yd_available = self.long_yd - self.long_yd_frozen
+
+        # If there is td_volume, we can only lock position
+        if td_volume:
+            req_open = copy(req)
+            req_open.offset = Offset.OPEN
+            return [req_open]
+        # If no td_volume, we close opposite yd position first
+        # then open new position
+        else:
+            open_volume = max(0, yd_available - req.volume)
+            req_list = []
+
+            if yd_available:
+                req_yd = copy(req)
+                if self.exchange == Exchange.SHFE:
+                    req_yd.offset = Offset.CLOSEYESTERDAY
+                else:
+                    req_yd.offset = Offset.CLOSE
+                req_list.append(req_yd)
+
+            if open_volume:
+                req_open = copy(req)
+                req_open.offset = Offset.OPEN
+                req_open.volume = open_volume
+                req_list.append(req_open)
+
+            return req_list