For the sensorless high-speed permanent magnet synchronous motor (HSPMSM) system with harsh operating environment, the parameter dependence of the sensorless algorithm deserves to disscuss. A position sensorless algorithm based on estimating the extended back electromotive force (EMF) in a rotating coordinate system is studied, and the system stability analysis method is used to qualitatively analyze the motor parameter dependence of the algorithm. By establishing a fourth-order extended Kalman observer to identify the motor parameters online and combining the parameter dependence law, the motor parameters in the position observer algorithm model are adjusted in real time, which effectively solves the problem of system instability caused by parameter changes during operation. The effectiveness of the method proposed is verified on the high-speed centrifugal compressor control platform with rated power and speed of 60 kW and 45 000 r/min, respectively.