The design goal of the large-diameter reflector used in the space remote sensor is high specific stiffness. In order to limit the launch costs, reduce the mass of reflector as far as possible and ensure the function requirements of the reflector, improve the structure stiffness of the reflector itself as much as possible, the reflector lightweight design is more important along with the rise of the reflector aperture. In this paper, aimed at the lightweight design of some Ф2 m-level space-based large-diameter reflector, the integrated optimization design method, which was a combining method with the traditional experience design, the topology optimization design and the size parameter optimization design, was applied. Compared with traditional optimization design method of the large-diameter reflector, it can make the design result fast converge, getting the optimal design structure. The mass of the Ф2 m reflector designed with the integrated optimization design method was 326 kg, the lightweight rate of the Ф2 m reflector was as high as 82.5%, the shape error variation RMS of the reflector which characterized the image quality of reflector and depended on the reflector stiffness was 4.9 nm when the reflector optical axis was vertical and the gravity load of 1 g was applied, and 4.3 nm when the reflector optical axis was horizontal and the gravity load of 1 g was applied. The results show that the mass of the reflector is smaller than the design requirement of 340 kg, and that the shape error variation RMS is better than the design requirement of 5 nm, satisfying the requirement of the high specific stiffness of the reflector.