Because of the good performance, PMSM is applied widely, and sensorless control of PMSM drive system has attracted much attention. In this work, sensorless control of Interior PMSM (IPMSM) was implemented by using Model Reference Adaptive System (MRAS) method, then the sensorless control of wide-speed-range, from stand still to high levels beyond the rated speed (3 times higher than the rated speed), was achieved by incorporating field-weakening and decoupling control technique. In the end, the experimental results exhibit good performance.