Systematically adopting strict control over the processing and assembly accuracy of optical elements, adopting high-quality and stable opto mechanical structure, and using precision thermal control are the conventional methods to ensure the high performance imaging quality of the optical system of space cameras in the past, but at the same time, the implementation of this strategy also brings high economic and resource costs to camera development. In the face of the development trend of low-cost high-performance space optical cameras, reducing the error sensitivity of the optical system and lowering the implementation cost while ensuring the imaging performance are the issues that need to be faced and solved. In this paper, a compact space camera as a background, and the low error-sensitivity design method (desensitization design method) is applied to a coaxial two-mirror catadioptric optical system with a focal length of 500 mm, a relative aperture of 1 : 5, and a field of view of 2.75°×2.75°. The results show that the optical system, based on the desensitized design method, not only gets excellent aberration correction theoretical results and modulation transfer function which is close to the diffraction limit, but also shows that the optical system is robust under the error interference in the simulation, which provides a guarantee for the rapid and low-cost manufacturing of the camera. The optical system desensitization design method has an important application value for the design and rapid development of high-performance small space loads at low cost.