The invention discloses a method for simulating multi-CUP synchronous operation of a relay protection device through a PC. Synchronous execution of multiple CPU plug-in protection tasks in the relay protection device is achieved in a simulated mode on the PC. A producer and customer model is used, and a mechanism which simulates data input and synchronous operation of virtual CPUs is built, wherein a management module serves as a producer to be responsible for providing simulated operation data for the virtual CPUs, storing forwarded and shared data and coordinating synchronous execution of protection tasks in the CPUs; the virtual CPUs serve as customers to be responsible for reading the simulated data and executing the protection tasks. A simulation system obtained on the basis of the method guarantees accuracy of operation results, solves the problem that debugging and development of protection logic heavily depend on hardware devices, provides rich debugging measures, and can effectively shorten the research and development cycle of the protection device.