The gimbal servo system for a Control Moment Gyroscope(CMG) directly driven by a Permanent Magnet Synchronous Motor (PMSM) was designed, and an Active Disturbance Rejection Control( ADRC) algorithm with integral feedback was proposed. Firstly, the mathematic model for the CMG gimbal servo system was built by using an oriented control strategy in shaft current id=0. Then, the effects of both frictional and alveolar torques on the performance of gimbal servo system were analyzed. A simulation system for gimbal servo system which used the ADRC as a speed loop was built up in Matlab. Finally, the hardware experiments of fuzzy PI, ADRC and the ADRC with integral feedback were carried out. Test and experiments show that the steady state accuracy is 0.005-0.012 rad/s when a step velocity of 0.1-2.0 rad/s is tracked by using the ADRC., and that is 0.001-0.005 rad/s and the crawling speed is 0.003 rad/s when the step velocity of 0.0-0.1 rad/s is tracked by using the ADRC with integral feedback. Furthermore, the relative amplitude error is 0.55% and the phase error is 0.099 78 rad, when the gimbal system tracks the 2sin(t) rad/s by using the ADRC with integral feedback. The proposed gimbal servo system of CMG satisfies the demands of high precision and robustness.