Abstract: To improve dynamic and static performance of inertia momentum wheels,its rotational speed tracking and output torque precision,a novel sliding mode variable-structure control algorithm was presented.The state-space average model for inertia momentum wheels was established,that consisted of permanent magnet brushless DC motor and power convertor.Based the reach qualification expressed by Lee differential coefficient,the sliding mode variable-structure control law was designed and deduced.The experimentations were performed on inertia momentum wheels to validate the effectiveness of the proposed control law.Experimental results demonstrated that the proposed algorithm made the winding current smooth,improved the rotational speed tracking precision from 2.51 rad/s to 0.21 rad/s and output torque precision from 0.01 N?m to 0.001 N?m,and possessed faster response,smaller over-shoot,better dynamic and static performance.