diff --git a/vnpy/api/rest/rest_client.py b/vnpy/api/rest/rest_client.py
index b0806278..0d0260f6 100644
--- a/vnpy/api/rest/rest_client.py
+++ b/vnpy/api/rest/rest_client.py
@@ -1,7 +1,9 @@
+import logging
 import multiprocessing
 import os
 import sys
 import traceback
+import uuid
 from datetime import datetime
 from enum import Enum
 from multiprocessing.dummy import Pool
@@ -10,6 +12,8 @@ from typing import Any, Callable, List, Optional, Union
 
 import requests
 
+from vnpy.trader.utility import get_file_logger
+
 
 class RequestStatus(Enum):
     ready = 0  # Request created
@@ -105,21 +109,35 @@ class RestClient(object):
         """
         """
         self.url_base = ''  # type: str
-        self._active = False
+        self.logger: Optional[logging.Logger] = None
 
         self.proxies = None
 
+        self._active = False
+
         self._tasks_lock = Lock()
         self._tasks: List[multiprocessing.pool.AsyncResult] = []
         self._sessions_lock = Lock()
         self._sessions: List[requests.Session] = []
 
-    def init(self, url_base: str, proxy_host: str = "", proxy_port: int = 0):
+    def init(self,
+             url_base: str,
+             proxy_host: str = "",
+             proxy_port: int = 0,
+             log_path: Optional[str] = None,
+             ):
         """
         Init rest client with url_base which is the API root address.
         e.g. 'https://www.bitmex.com/api/v1/'
+        :param url_base:
+        :param proxy_host:
+        :param proxy_port:
+        :param log_path: optional. file to save log.
         """
         self.url_base = url_base
+        if log_path is not None:
+            self.logger = get_file_logger(log_path)
+            self.logger.setLevel(logging.DEBUG)
 
         if proxy_host and proxy_port:
             proxy = f"{proxy_host}:{proxy_port}"
@@ -257,6 +275,11 @@ class RestClient(object):
         )
         return text
 
+    def _log(self, msg, *args):
+        logger = self.logger
+        if logger:
+            logger.debug(msg, *args)
+
     def _process_request(
         self, request: Request
     ):
@@ -265,19 +288,32 @@ class RestClient(object):
         """
         try:
             with self._get_session() as session:
+                # sign
                 request = self.sign(request)
 
+                # send request
                 url = self.make_full_url(request.path)
+                uid = uuid.uuid4()
 
+                method = request.method
+                headers = request.headers
+                params = request.params
+                data = request.data
+                self._log("[%s] sending request %s %s, headers:%s, params:%s, data:%s",
+                          uid, method, url,
+                          headers, params, data)
                 response = session.request(
-                    request.method,
+                    method,
                     url,
-                    headers=request.headers,
-                    params=request.params,
-                    data=request.data,
+                    headers=headers,
+                    params=params,
+                    data=data,
                     proxies=self.proxies,
                 )
                 request.response = response
+                self._log("[%s] received response from %s:%s", uid, method, url)
+
+                # check result & call corresponding callbacks
                 status_code = response.status_code
                 if status_code // 100 == 2:  # 2xx codes are all successful
                     if status_code == 204:
diff --git a/vnpy/api/websocket/websocket_client.py b/vnpy/api/websocket/websocket_client.py
index e7c767a0..d89529a4 100644
--- a/vnpy/api/websocket/websocket_client.py
+++ b/vnpy/api/websocket/websocket_client.py
@@ -1,14 +1,18 @@
 import json
+import logging
+import socket
 import ssl
 import sys
 import traceback
-import socket
 from datetime import datetime
 from threading import Lock, Thread
 from time import sleep
+from typing import Optional
 
 import websocket
 
+from vnpy.trader.utility import get_file_logger
+
 
 class WebsocketClient(object):
     """
@@ -47,19 +51,36 @@ class WebsocketClient(object):
 
         self.proxy_host = None
         self.proxy_port = None
-        self.ping_interval = 60     # seconds
+        self.ping_interval = 60  # seconds
         self.header = {}
 
+        self.logger: Optional[logging.Logger] = None
+
         # For debugging
         self._last_sent_text = None
         self._last_received_text = None
 
-    def init(self, host: str, proxy_host: str = "", proxy_port: int = 0, ping_interval: int = 60, header: dict = None):
+    def init(self,
+             host: str,
+             proxy_host: str = "",
+             proxy_port: int = 0,
+             ping_interval: int = 60,
+             header: dict = None,
+             log_path: Optional[str] = None,
+             ):
         """
+        :param host:
+        :param proxy_host:
+        :param proxy_port:
+        :param header:
         :param ping_interval: unit: seconds, type: int
+        :param log_path: optional. file to save log.
         """
         self.host = host
         self.ping_interval = ping_interval  # seconds
+        if log_path is not None:
+            self.logger = get_file_logger(log_path)
+            self.logger.setLevel(logging.DEBUG)
 
         if header:
             self.header = header
@@ -109,6 +130,11 @@ class WebsocketClient(object):
         self._record_last_sent_text(text)
         return self._send_text(text)
 
+    def _log(self, msg, *args):
+        logger = self.logger
+        if logger:
+            logger.debug(msg, *args)
+
     def _send_text(self, text: str):
         """
         Send a text string to server.
@@ -116,6 +142,7 @@ class WebsocketClient(object):
         ws = self._ws
         if ws:
             ws.send(text, opcode=websocket.ABNF.OPCODE_TEXT)
+            self._log('sent text: %s', text)
 
     def _send_binary(self, data: bytes):
         """
@@ -124,6 +151,7 @@ class WebsocketClient(object):
         ws = self._ws
         if ws:
             ws._send_binary(data)
+            self._log('sent binary: %s', data)
 
     def _create_connection(self, *args, **kwargs):
         """"""
@@ -184,6 +212,7 @@ class WebsocketClient(object):
                             print("websocket unable to parse data: " + text)
                             raise e
 
+                        self._log('recv data: %s', data)
                         self.on_packet(data)
                 # ws is closed before recv function is called
                 # For socket.error, see Issue #1608
diff --git a/vnpy/trader/utility.py b/vnpy/trader/utility.py
index 38a6e7db..51471b70 100644
--- a/vnpy/trader/utility.py
+++ b/vnpy/trader/utility.py
@@ -3,8 +3,9 @@ General utility functions.
 """
 
 import json
+import logging
 from pathlib import Path
-from typing import Callable
+from typing import Callable, Dict
 from decimal import Decimal
 
 import numpy as np
@@ -14,6 +15,9 @@ from .object import BarData, TickData
 from .constant import Exchange, Interval
 
 
+log_formatter = logging.Formatter('[%(asctime)s] %(message)s')
+
+
 def extract_vt_symbol(vt_symbol: str):
     """
     :return: (symbol, exchange)
@@ -461,3 +465,25 @@ def virtual(func: "callable"):
     that can be (re)implemented by subclasses.
     """
     return func
+
+
+file_handlers: Dict[str, logging.FileHandler] = {}
+
+
+def _get_file_logger_handler(filename: str):
+    handler = file_handlers.get(filename, None)
+    if handler is None:
+        handler = logging.FileHandler(filename)
+        file_handlers[filename] = handler  # Am i need a lock?
+    return handler
+
+
+def get_file_logger(filename: str):
+    """
+    return a logger that writes records into a file.
+    """
+    logger = logging.getLogger(filename)
+    handler = _get_file_logger_handler(filename)  # get singleton handler.
+    handler.setFormatter(log_formatter)
+    logger.addHandler(handler)  # each handler will be added only once.
+    return logger