Abstract: The 3G, 4G and other wireless signals along the urban rail transit are increasingly causing serious interference to the subway communication based train control (CBTC) train-to-ground communication system in the adjacent frequency band 2.4G. In order to identify the interference source, the location technology of the interference source of the CBTC system has become an urgent problem to be studied. An received signal strength indicator (RSSI) ranging and positioning algorithm based on particle swarm optimization was proposed, which could effectively and quickly locate the interference source. The simulation results showed that when simulating trains with different running speeds, the accuracy of the algorithm for locating interference sources was different. It is concluded that the algorithm has higher accuracy for locating interference sources of trains with lower operating speed.