Abstract: Magnetically suspended control moment gyro (MSCMG) is the primary attitude actuator of large spacecraft, and the MSCMG gimbal servo system control precision is one of the main factors which affect gyroscopic torque accuracy. In order to enhance the MSCMG gimbal servo system disturbance suppression ability and control precision, a disturbance observer based on angular acceleration for MSCMG gimbal servo system was proposed. Using angle, Kalman filter estimates the velocity, which was sent to the state observer to acquire the precise angular acceleration. Angular acceleration and current were used as inputs of disturbance observer to obtain compensatory current. Then the compensatory current was sent to the input of current loop to compensate various disturbances. The disturbance observer has characteristics of simple structure and good disturbance suppression ability. The experimental result shows that this method can effectively improve the velocity precision and stability of the MSCMG gimbal servo system.