A focusing mechanism with a tilt of focusing plane assembly less than 7 ", positioning accuracy better than 0.01 mm in the ±2 mm focusing range was designed to ensure the best image quality for a wide field space camera with a focal plane length more than 600 mm. To meet the requirements of the focusing mechanism for focusing accuracy, mechanical environments and the vacuum environments, the dual-cam drive technology was used to complete the accurate focusing, and the loss of power brake self-locking technology allowed the camera to be a stable image plane position under the impact of mechanical environments. Furthermore, the high stiffness rail and bearings were used in the focusing mechanism to obtain a high dynamic stiffness. The design analysis and experimental results show that the dual focal plane cam-driven focusing mechanism has high focusing precision and high reliability and is able to complete the focuing and improve the image quality of space cameras in the complex space environments.