The utility model discloses a semi-physical simulation system of a PM (permanent-magnet) SM (synchronous motor) servo controller, which comprises a PC (personal computer), a signal converter and a PM SM servo controller, wherein the signal converter is used for converting digital signals and analog signals between the PC and the PM SM servo controller; the PC sends control parameters of a PM SM model to the PM SM servo controller for processing; the processing result is returned to the PC through the signal converter to control the PM SM model, and meanwhile, the PC acquires a current state parameter of the PM SM model and adjusts the control parameters of the PM SM model according to the current state parameter; the signal converter comprises a main control chip, a download communication chip and a USB (universal serial bus)-to-serial-port chip; the download communication chip is connected with the main control chip; and the PC is connected with the download communication chip through the USB-to-serial-port chip. According to the utility model, the information communication between the PM SM mathematical model constructed in the PC and the PM SM controller can be realized, and a closed-loop physical environment which approximate to engineering reality and is easy to verify can be formed. Besides, the semi-physical simulation system is low in development cost and is simple and easy to implement.