Abstract: The sensorless control technology based on the Luenberger observer was commonly used for surface mounted permanent magnet synchronous motors. The key to the Luenberger observer lied in the design of the feedback matrix. In order to simplify the process of solving the feedback matrix, it was common to ignore changes in rotor position or directly set certain coefficients in the feedback matrix to zero. However, this not only deteriorated the observer’s performance of rotor position but also increased debugging time. Therefore, by comparing the coefficients of the characteristic equation, a detailed expression of the feedback matrix was designed, which only required adjusting one parameter of the pole left shift distance, greatly shortening the debugging process. Simulation studies show that compared to feedback matrices that ignore changes in rotor position, the feedback matrix designed in this way has better steady-state accuracy.