This paper studies the technology of permanent magnet synchronous motor with direct torque control. Firstly, the mathematical models of PMSM in three-phase static reference frame, two-phase static reference frame and two-phase rotating reference frame are derived. The basic working principle of direct torque control technology is understood. Secondly, the direct torque control technology with a rotor position sensor is analyzed, because there is no iteration the calculating the stator flux linkage and electromagnetic torque, the dynamic response speed of electric torque can be very fast, but this technology depends heavily on motor parameters and rotor position. Finally, direct torque control simulation under d-q frame as well as the α-β frame is evaluated, and also evaluated are sensored and sensorless control scheme. A comprehensive investigation of speed regulation and sensorless direct torque control performance are carried out via the simulation.