With the continuous advancement of optical imaging technology and the increasing requirement for remote sensing applications, high-resolution spatial imaging technology has been extensively researched. Subject to the diffraction limitation, the optical aperture is continuously increasing to obtain more target details, which leads to larger satellite platforms and higher manufacturing costs. In order to balance the cost of satellite platforms and the imaging quality of space cameras, this paper focuses on the optical aperture, which affects both of the above by conducting an end-to-end analysis of the space imaging process to examine its effects on overall imaging spatial quality. This paper formulates the optical aperture optimization problem by establishing the evaluation functions for deployment cost and imaging quality. Two types of optical systems commonly used in space imaging, the coaxial reflective optical system with annular aperture and the topologically compact optical system with square aperture are studied based on the proposed optimization model. Their imaging characteristics and design principles are summarized. The optimization model proposed can be applied to the optical aperture design of any manufacturable optical system to guide the design of the entire space camera and even the satellite platforms.