Aiming at the problems that the rotor speed and position are difficult to be accurately estimated by the sliding mode observer (SMO) due to high frequency chattering, and the robustness and speed tracking performance of the speed loop PI controller are poor, an improved SMO-based speed sensorless control for permanent magnet synchronous motor(PMSM) is proposed. First, an infinite impulse response(IIR) filter is added to the sliding mode observer in the direct torque control(DTC) system to deal with the high frequency noise in the output of the sliding mode observer, Then a continuous hyperbolic tangent function is adopted to replace the discontinuous sign function to attenuate the system chattering. Moreover, an active disturbance rejection control(ADRC)-based speed loop controller is to improve the confliction between the overshoot and settling time of the system. Finally, a hardware-in-the-loop experimental platform is built in Matlab/Simulink environment. The simulation and experimental results show that under the same load and interference conditions, compared with the traditional speed sensorless control-system, the proposed speed sensorless ADRC-based controller can suppress the chattering effectively and exhibits better robustness and speed tracking performance.