Now encryption adjustment wells are getting widely used in offshore, and the risk of well collision increases greatly. Well anti-collision is becoming more and more important. An anti-collision monitoring system based on detecting casing head vibration induced by drilling movements has been build and rig-site utilized. The acceleration sensors were fixed on the casing head to fell the vibration, the time domain analysis and frequency domain analysis were used in signal processing to recognize the approach motive of the drilling bit to the risk case of production well. The result of rig-site test shows that the newly disigned monitoring system can recognize the vibration caused by bit work and detecting the drilling bit approaching the case. It also indicates that the anti-collision monitoring system for detecting casing head vibration is practicable.