In the observation of large survey telescopes， the camera is required to expose designated sky area for a long time. The long exposure image is rotated due to the Earth’s rotation. The derotator is used to counteract the impact of the Earth's rotation on the imaging quality， ensuring stable position and energy concentration of the imaging spot on the camera. Camera rotation method is used as the derotator of Mozi sky survey telescope. The derotator requires a bearing capacity of ≥ 250 kg， a speed of >20′/s， and an angular positioning accuracy of ≤ 2″. This article analyzed the factors that affect the load-bearing capacity， rotational speed， and positioning accuracy of the derotator. High-precision turntable bearing combined with lightweight rotating shaft were adopted to achieve high-precision and high stiffness shaft in this paper. The shaking of the shaft system was 1.9″. The transmission system adopted a harmonic reducer combined with a cylindrical spur gear pair for two-stage transmission， achieving low speed and high angular resolution. The absolute circular grating with dual reading head was used to measure the angle error. The compensated angle positioning accuracy was better than 1.1″. The survey image with concentrated energy spot and no image rotation after the compensation of the derotator. The Mozi sky survey telescope achieves the goal of high-quality imaging.