A Robust Iterative Learning Control (RILC) method by combining sliding mode control with Iterative Learning Control (ILC) was proposed to suppress the effect of torque ripples on control system and to improve the performance of speed servo system in a Permanent Magnet synchronous Motor(PMSM) . An iterative learning controller was designed to reduce the periodic torque ripples and a sliding mode controller was used to guarantee the fast response and strong robustness to further enhance the anti-disturbance ability of the system. Verification experiments were carried out, and the results demonstrate that when the motor is operating at a speed of 900 r/min, the robust ILC reduces the 6th harmonics amplitude from 0.89 to 0.56. When a sudden load 0.5 N·m is added to the system, the robust ILC gives a maximum speed fluctuation of 22 r/min. Compared with PI-ILC, the speed fluctuation is reduced by 1.4%. When the motor is operating at a speed of 60 r/min, the robust ILC reduces the 6th harmonics amplitude from 4.87 to 0.45. When a sudden load 0.5 N·m is added to the system, the robust ILC gives a maximum speed fluctuation of 24 r/min. Compared with that of a PI-ILC, the speed fluctuation is reduced by 23%. The experimental results indicate that the proposed robust ILC method improves the dynamic and robust performance of the speed servo system and suppresses the periodic torque ripples effectively.