Abstract: Aiming at the hidden danger of railway safety, this paper introduced the third generation Beidou satellite navigation system (Beidou third generation for short) high-precision positioning technology into railway monitoring and early warning, designed the railway monitoring and early warning system based on Beidou third Generation. The system used the principle of Beidou high-precision positioning to implement high-precision monitoring of displacement data, and had real-time transmission and instant warning functions. Practice has proved that the system has obvious advantages over the GPS based monitoring and early warning system, with a significant increase in the number of visible satellites, an increase in horizontal accuracy of more than 20%, and an increase in elevation accuracy of more than 50%. Through the comparison of monitoring performance under different baseline lengths, it provides a reference for the reasonable deployment of reference stations.