Abstract: The control system of sensorless of permanent magnet synchronous motor is the study hot-spot because it has many advantages such as high precision in control,convenience in installation and maintenance and high reliability. The working principle of sensorless control technology of permanent magnet synchronous motor was introduced in the paper,and its study status was analyzed. Through analysis and comparing of its control strategy, the present study focus and problems needed to be solved of sensorless control technology of permanent magnet synchronous motor were put forward.