An integrated ultra-light main supporting structure is designed to satisfy the ultra-light, low-power consumption, short-period, and low-cost requirements of a particular micro-nano remote-sensing camera. After comparison with other materials and based on the design requirements, titanium alloy is selected as the research and development focus, and a truss scheme is selected considering mass and power consumption. A mathematical model of topology optimization with fundamental frequency as the objective function is established. In addition, the sensitivity of the objective function is derived, and an improved Heaviside density filter is adopted. As a result, the optimal load path with clear topological results is obtained. Similarly, to obtain the optimal size of each part, a mathematical model of size optimization with fundamental frequency as the objective function is established. Eventually, the mass of the proposed structure is 0.6 kg. The results of finite element analysis and test demonstrate that the integrated main supporting structure can satisfy the tolerance requirement of an optical system and that the fundamental frequency is much higher than the optical load requirement of a satellite platform, which verifies the correctness and rationality of the proposed optimization design.