Mechanical structure, of which a trade-off between weight and strength has always been considered primely, is important for a space camera as a hub for other assemblies such as optics parts, electronic parts, etc. Traditionally the space camera is composed of a nearly line-up of arrangements containing different units, which is easy to assemble and manufacture, however, not a good type for mechanical properties due to the cantilever structure. We present a new type of unitized design for the structure of the space camera, which unite the tube and the electric cabinet as one unit, with the PCBs (Printed Circuit Boards) surrounded. The main frame is optimized by using topology optimization, improving the characteristic of the structure. The maneuverability has also been considered. Compared with some traditional type, the new type proved to be lighter and more compact, which is beneficial to the mechanical properties and the cost control of satellite launching.