The interoperability of CBTC (communication-based train control system) has shown great advantages and become an important development trend in the construction and operation of urban rail transit systems. In order to satisfy the emerging interoperability requirements, the overall function of the computer interlocking system is divided into logic processing functions and communication functions, which are processed respectively by the safety communication board and the CPU board. The interoperable computer interlocking system has multiply functions of data synchronization between the double CPUs in a single system, master-slave synchronization between two systems, system state management, safety communication, and complex safety protocol processing. Finally, system test results in Chongqing interoperability laboratory verify the availability of interoperable computer interlock systems. The realization will promote upgrading of other signaling systems and improve the performance of the overall CBTC system.