The system adopts advanced machine vision dynamic analysis technology, calculates the size and shape of the foreign matter invading the limit through the real-time dynamic analysis of the video image of the monitoring point, and gives an alarm for the foreign matter invading the limit beyond the threshold, which can effectively monitor the damage of the railway line and the interference to the driving caused by natural disasters and foreign matter invasion. The system has high accuracy, strong reliability, wide detection range and intuitive detection results. It is applicable to the safety monitoring of key areas of main line and tunnel entrance.