Abstract: Urban rail transit signaling system plays an important role in ensuring safe and highly efficient operation of train, and in elevating automation level of train command. With large scale of urban rail transit line network construction and operation, problems existing in typical CBTC (communication based train control) system architecture have become increasingly evident, such as insufficient refinement of resource allocation, difficult to implement agile function;large investment of fallback system together with low utilization efficiency and ROI (return of investment); poor system robustness; difficulty in upgrading and retrofit and the high cost of system construction, operation and maintenance. Through enhancement of CBTC system architecture, the above problems can be ameliorated. Simplified CBTC system architecture and TACS (train autonomous control system) architecture have made improvement targeting the problems existing in typical CBTC system architecture. By comprehensively analyzing the main characteristics of the two (advantages and technical maturity) and the application status, conclusions are obtained that currently, the simplified CBTC system architecture has become relatively mature for large-scale promotion, while the TACS architecture is still in the initial stage of application. The fallback system design for the operation scenario under failure conditions must be carefully considered in high-density line application.