diff --git a/docs/conf.py b/docs/conf.py
index add10ce..4c9bb0e 100644
--- a/docs/conf.py
+++ b/docs/conf.py
@@ -13,9 +13,7 @@
 # All configuration values have a default; values that are commented out
 # serve to show the default.
 
-import sys
 import os
-import shlex
 
 # If extensions (or modules to document with autodoc) are in another directory,
 # add these directories to sys.path here. If the directory is relative to the
diff --git a/hbmqtt/broker.py b/hbmqtt/broker.py
index 6d5dcaf..b5c5b39 100644
--- a/hbmqtt/broker.py
+++ b/hbmqtt/broker.py
@@ -7,7 +7,7 @@ import websockets
 import asyncio
 import sys
 import re
-from asyncio import Queue, CancelledError
+from asyncio import CancelledError
 from collections import deque
 
 from functools import partial
diff --git a/hbmqtt/client.py b/hbmqtt/client.py
index a5bf8d9..b213ef5 100644
--- a/hbmqtt/client.py
+++ b/hbmqtt/client.py
@@ -14,7 +14,7 @@ from hbmqtt.mqtt.connect import *
 from hbmqtt.mqtt.protocol.client_handler import ClientProtocolHandler
 from hbmqtt.adapters import StreamReaderAdapter, StreamWriterAdapter, WebSocketsReader, WebSocketsWriter
 from hbmqtt.plugins.manager import PluginManager, BaseContext
-from hbmqtt.mqtt.protocol.handler import EVENT_MQTT_PACKET_SENT, EVENT_MQTT_PACKET_RECEIVED, ProtocolHandlerException
+from hbmqtt.mqtt.protocol.handler import ProtocolHandlerException
 from hbmqtt.mqtt.constants import *
 import websockets
 from websockets.uri import InvalidURI
diff --git a/hbmqtt/mqtt/connack.py b/hbmqtt/mqtt/connack.py
index a19f2b7..074fd8e 100644
--- a/hbmqtt/mqtt/connack.py
+++ b/hbmqtt/mqtt/connack.py
@@ -3,7 +3,7 @@
 # See the file license.txt for copying permission.
 import asyncio
 from hbmqtt.mqtt.packet import CONNACK, MQTTPacket, MQTTFixedHeader, MQTTVariableHeader
-from hbmqtt.codecs import int_to_bytes, read_or_raise, bytes_to_int
+from hbmqtt.codecs import read_or_raise, bytes_to_int
 from hbmqtt.errors import HBMQTTException
 from hbmqtt.adapters import ReaderAdapter
 
diff --git a/hbmqtt/mqtt/protocol/client_handler.py b/hbmqtt/mqtt/protocol/client_handler.py
index d29767f..5e37f2f 100644
--- a/hbmqtt/mqtt/protocol/client_handler.py
+++ b/hbmqtt/mqtt/protocol/client_handler.py
@@ -5,7 +5,6 @@ import asyncio
 from asyncio import futures
 import sys
 from hbmqtt.mqtt.protocol.handler import ProtocolHandler, EVENT_MQTT_PACKET_RECEIVED
-from hbmqtt.mqtt.packet import *
 from hbmqtt.mqtt.disconnect import DisconnectPacket
 from hbmqtt.mqtt.pingreq import PingReqPacket
 from hbmqtt.mqtt.pingresp import PingRespPacket
diff --git a/hbmqtt/mqtt/subscribe.py b/hbmqtt/mqtt/subscribe.py
index 1878aa9..0a2a9b2 100644
--- a/hbmqtt/mqtt/subscribe.py
+++ b/hbmqtt/mqtt/subscribe.py
@@ -2,7 +2,7 @@
 #
 # See the file license.txt for copying permission.
 from hbmqtt.mqtt.packet import MQTTPacket, MQTTFixedHeader, SUBSCRIBE, PacketIdVariableHeader, MQTTPayload, MQTTVariableHeader
-from hbmqtt.errors import HBMQTTException, MQTTException
+from hbmqtt.errors import HBMQTTException
 from hbmqtt.codecs import *
 
 
diff --git a/tests/plugins/test_manager.py b/tests/plugins/test_manager.py
index 312e2ec..92e54cf 100644
--- a/tests/plugins/test_manager.py
+++ b/tests/plugins/test_manager.py
@@ -4,7 +4,7 @@
 import unittest
 import logging
 import asyncio
-from hbmqtt.plugins.manager import PluginManager, BaseContext
+from hbmqtt.plugins.manager import PluginManager
 
 formatter = "[%(asctime)s] %(name)s {%(filename)s:%(lineno)d} %(levelname)s - %(message)s"
 logging.basicConfig(level=logging.INFO, format=formatter)
diff --git a/tests/plugins/test_persistence.py b/tests/plugins/test_persistence.py
index 580fbbf..de259d6 100644
--- a/tests/plugins/test_persistence.py
+++ b/tests/plugins/test_persistence.py
@@ -9,7 +9,6 @@ import asyncio
 import sqlite3
 from hbmqtt.plugins.manager import BaseContext
 from hbmqtt.plugins.persistence import SQLitePlugin
-from hbmqtt.session import Session
 
 formatter = "[%(asctime)s] %(name)s {%(filename)s:%(lineno)d} %(levelname)s - %(message)s"
 logging.basicConfig(level=logging.DEBUG, format=formatter)
diff --git a/tests/test_broker.py b/tests/test_broker.py
index 407fd1d..fa031df 100644
--- a/tests/test_broker.py
+++ b/tests/test_broker.py
@@ -2,7 +2,7 @@
 #
 # See the file license.txt for copying permission.
 import unittest
-from unittest.mock import patch, call, MagicMock
+from unittest.mock import patch, call
 from hbmqtt.broker import *
 from hbmqtt.mqtt.constants import *
 from hbmqtt.client import MQTTClient, ConnectException
diff --git a/tests/test_client.py b/tests/test_client.py
index 0050385..905ade8 100644
--- a/tests/test_client.py
+++ b/tests/test_client.py
@@ -8,7 +8,6 @@ import logging
 from hbmqtt.client import MQTTClient, ConnectException
 from hbmqtt.broker import Broker
 from hbmqtt.mqtt.constants import *
-from hbmqtt.errors import HBMQTTException
 
 formatter = "[%(asctime)s] %(name)s {%(filename)s:%(lineno)d} %(levelname)s - %(message)s"
 logging.basicConfig(level=logging.ERROR, format=formatter)
diff --git a/tox.ini b/tox.ini
index a549f08..d6c9d0e 100644
--- a/tox.ini
+++ b/tox.ini
@@ -1,6 +1,5 @@
 [flake8]
 ignore =
-    F401,  # 'x' imported but unused (~12 warnings)
     F403,  # 'from x import *' used; unable to detect undefined names (~29 warnings)
     F821,  # undefined name 'x' (~1 warnings)
     F841,  # local variable 'wildcard_pattern' is assigned to but never used (~17 warnings)