Abstract: In view of the defect of long monitoring period, low monitoring precision and no realtime automatic monitoring existed in mine slope monitoring method, an online monitoring and early warning system of mining slope stability was designed, and design principle and structure of the system were introduced. The system can monitor change states of displacement field of rock slope in mining process, and can transmit the monitored data to host computer by wireless network, so as to realize visualization of monitoring data. The system also has early warning function, and can set warning threshold according to the need. The system can automaticly alarm when the slope displacement exceeds the warning threshold. The practical application proves reliability of the system.