Abstract: Aiming at the risks brought by the promotion of interoperable CBTC (communication based train control) system in urban rail transit, the safety assessment appears vital in particular as an important supervision process. Based on an analysis of the represented interoperation CBTC system architectures in Chongqing and New York, the assessment systems of both are compared from aspects of safety assessment standards, hazard assessment methods, safety certification process and activities. Combined with their interoperation CBTC characteristics and application scenarios, appropriate safety assessment rules are developed, and the established system safety goals are achieved through different methods and approaches.