To solve the problems of low precision of the observation of speed and rotor position and large torque ripple in the direct torque control system of permanent magnet synchronous motor, a new sliding mode observer based on the combination of variable exponential approach law and phase-locked loop technique was proposed. Variable exponential approach law was used to improve the accuracy of back EMF observation and proved its stability. Switching function was replaced by continuous function to reduce chattering. Phase-locked loop technology was applied to extract speed and rotor position information. On this basis, the motor discretization model was established to derive the flux linkage and torque deadbeat control law. The deadbeat controller was designed to furtuer alleviate chattering and improves the system control performance. The simulation results show that the strategy can observe the rotational speed and rotor position accurately, suppress the ripple of the flux linkage and torque effectively, and improve the dynamic of the system.