This paper introduces a new adaptive speed estimator based sensorless control algorithm for speed control of Permanent Magnet Synchronous Motor (PMSM). The algorithm is based on Field Oriented Control (FOC) theory. In this control algorithm, the rotor speed and position feedbacks are obtained using a model reference adaptive system estimator. Also a load torque estimator is adapted to improve the control algorithm performance in speed control. Maximum Torque per Amper (MTPA) control strategy is employed in the proposed algorithm forthe speeds lower than base speed. Both the proposed control and conventional control structures are simulated usingMatlab/Simulink. Simulation results showed the some advantages of the proposed control algorithm compared to the conventional its.