The classical direct torque control (DTC) system of three phase induction motor suffers from many drawbacks such as the need for motor speed sensor, flux and torque ripples, and constancy of the stator resistance in the DTC controller. In this paper a sensorless system based on Model Reference Adaptive System (MRAS) is designed to estimate the rotor speed without using encoder. The classical and MRAS systems are compared. Computer simulation proves the effectiveness and robustness of the proposed MRAS for estimating the motor speed over the classical one.