For a structure design of a space camera’s reflector, the reflector’s characteristic is big rectangle and big caliber. Based on optimization material, analyze rectangle reflector’s support characteristic, study reflector’s support theory, put forward a new flexible support based on half kinematics theory, namely a complex support form that three point on backside and three accessorial point, and analyze statics, dynamics and thermal characteristics by computer. It is tested that the project is reasonable and suitable for the big rectangle and big caliber reflector. We settle a difficult problem of the big rectangle and big caliber reflector’s support.