The chattering caused by using symbolic functions exists in the traditional sliding mode observer. In order to solve the problem, a synergetic observer method based on continuous function is proposed to realize the sensorless control of permanent magnet synchronous motor (PMSM). The discrete mathematical model of the PMSM is studied. The functional relationship between the current deviation at time k+1 and that at time k is established. The arctangent function calculates the rotor position and adds angle compensation to improve the observation accuracy. The simulation results show that the designed synergetic observer has no chattering and has higher estimation accuracy and good anti-interference performance. It can better realize the sensorless control of the PMSM than the traditional sliding mode observer.