Abstract: Focusing is one of the key technologies to improve the imaging quality in multispectral CCD camera. The design, realization, and performance of a focusing system for multispectral CCD camera were presented in detail, featuring wide field of view and wide swath wide with TMA optical system, based on earth observation satellite. First, the focusing precision required was calculated according to the shortest spectrum wave in the optical system. Compared with other focusing methods, the method of direct adjusting CCD focal plane was proposed, which was suitable for this CCD camera optical system. Second, a focusing system was developed, the hardware system including stepper motor, worm couple, pair of gears, precision screw ball, linear bearing, and encoder was constructed. And its theoretical focusing sensitivity was calculated to be 0.12 m, The proposed focusing system has the advantages of lower constructional complexity, easier hardware implementation and high focusing sensitivity. Finally, experimental setup was constructed to evaluate the focusing precision performance of the focusing system. The result of the experiment indicated the 3.62 m(3) precision of focusing in a range of 2.2 mm. And after mechanical vibration test and thermal vacuum test, the focusing precision was 3.64 m(3) precision of focusing in a range of 2.2 mm. The experimental result shows that the proposed focusing system is remarkable, reasonable, and reliability, as well as stable, which meet the focusing precision requirements for multispectral CCD camera.