Existing cosimulation techniques for cyber-physical power systems (CPPSs) suffer from a tradeoff between simulation accuracy and calculation speed. One of the most critical issues influencing the simulation performance is the method of synchronization between the two simulators. In this article, to efficiently solve the data interchange problem for asynchronous simulators, a state-caching-based synchronization mechanism is proposed to balance accuracy and efficiency. A state-caching module is designed to store the system’s status at critical moments and backtrack the simulation process when necessary; thus, nonessential data interactions are reduced. In addition, to solve the problems of processing multiple concurrent events and node mapping in CPPS modeling, a network boundary module is proposed that distributes and aggregates interface packets in accordance with the number of devices. Based on the above method, a State-Caching-based COsimulation (SCCO) platform is designed for CPPS evaluation, and the effectiveness and advantages of the proposed method are demonstrated based on simulated results for cyber-physical events.