Abstract: To compensate focusing offset of space camera, which was caused by environment difference between ground and on the track and maybe caused by shock when launching, a focal plane focusing device was designed to ensure image quality. First, for focal plane was so large, focusing frame was designed to enhance focal plane rigidity, self-lock was achieved through worm wheel driving screw. Second, fem model was established and mode analysis was achieved by patran/nastran, in which simulate guide rail by mpc. Finally, carried out dynamic environment testing and precision testing. Test results revealed that focusing device had dynamic frequency, first analysis characteristic frequency was 228.7 Hz, and first test characteristic frequency was 223.9 Hz, the relative error was 2%. Focusing resolution was 0.25 m, focusing precision was 6.3 m, synchronization error on focal plane was 4 m. It can meet high resolution, high precision, high reliability needs of space camera.