Abstract: CBTC (communication based train control) system is a widely applied signaling system in urban rail transit, in which the trainwayside wireless system is responsible for carrying train control information. The development trend and performance characteristics of 5G technology are introduced. The wireless communication requirements of CBTC system are analyzed. The performance of 5G bearing CBTC system service under different scenarios is tested at the elevated section of Shanghai Rail Line 5. Field test results show that the technical indicators of 5G bandwidth, endtoend delay, roaming and other aspects are higher than what CBTC system requires of wireless subsystem of data communication system, and in terms of technical performance, 5G can be used for the service bearing of CBTC system. Using 5G slicing function, 5G communication network can guarantee the service transmission of CBTC system in highest priority under extreme pressure, improving the high reliability of CBTC system service transmission.