In order to solve the problem of high cost，mounting volume increases，low reliability，being susceptible to interference and difficult to apply in a complex application environment caused by the traditional mechanical，there is find a new method based on the model reference adaptive (MRAS) control theory to estimate the rotor position and speed. Mathematical model of PMSM，speed closedloop control method and current sensorless control technology was studied. PMSM itself is considered as reference model and the stator current equations is considered as adjustable model containing variable speed. Adaptive law is designed based on Popov stability theory. As the result of the simulation proved that MRAS has a high estimation accuracy，good tracking performance，stable steadystate speed，good dynamic and static performance，and strong robustness towards speed variations and load disturbance of PMSM，this control is very simple and effective.