Aiming at wireless network attacks such as DoS attacks,rouge STA, rouge AP,WarDriving attacks and bruteforce attacks, a Lightweight Intrusion Detection System for WLAN is implemented by combining the misuse detection and anomaly detection. In this system,the user can define attack rule set, authorization AP/STA list, illegal AP/STA list, and the sensitivity and the threshold value of detection can adjust according to the circumstance and user requirement. The test shows that this system has a better detecting effect than other WLAN intrusion detection in market.