Abstract: Mathematical model of permanent magent synchronous motor(PMSM) and its vector control principle in d-q coordinate were analyzed and a method of applying EKF in PMSM sensorless control system was proposed. In α-β and d-p coordinates, nonlinear equations of PMSM were linearized and its rotor position and speed were estimated realtimely by EKF algorithm, so as to satisfy demand of realtime control. The results of Matlab/Simulink simulation and dSPACE hardware platform test showed that the PMSM sensorless control system based on EKF has steady running, small overshoot and perfect dynamic and static performance.