High-resolution space optical camera defocused in orbit due to the change of space operational environment, which would affect the image quality. Therefore, refocusing were required by the camera in orbit. In order to meet the requirements of high resolution and lightweight space optical camera, a main support structure with both support and refocusing function was designed. The position of the secondary mirror assembly was adjusted along the optical axis by the precise temperature control of the supporting structure, then the camera can be refocused by the thermal control of the supporting structure. Firstly, the refocusing accuracy was analyzed according to the optical system parameters to determine the design requirements of the support structure; Then, the global optimization of the supporting structure was performed based on the variable density of continuous topology optimization (SIMP); Finally, the thermal optical test was performed to verify the thermal refocusing function and measure the thermal refocusing parameters of the apace camera. The experimental results show that the thermal refocusing parameter of the supporting structure is 0.071 mm/℃, the refocusing accuracy and range are 0.014 mm and ±0.385 mm respectively. The proposed method had been used in the design of "Jilin-1"gf03 satellite which had been tested in orbit, and the focusing accuracy and focusing range meet the design expectations.