A simulation system of permanent magnet synchronous motor based on inverter is proposed in this paper, which can replace the actual motor and mechanical test platform in motor driver test. This paper adopts the Adams method to establish the mathematical model of the permanent magnet synchronous motor. The simulated motor can calculate the current state of the motor such as current and speed in real time. An improved internal model controller is used to control the inverter to accurately track the command current to ensure the speed and accuracy of the current tracking of the motor simulator. The designed Romberg torque estimation observer enables the motor to generate high-frequency pulsating torque to offset the fluctuation of the motor torque. The two typical working conditions of no-load start and sudden load are verified on the designed motor simulator. The simulation results show that the motor simulation system has good performance and can accurately and efficiently simulate the current of the motor port of the permanent magnet synchronous motor characteristic.