High-resolution imaging in space cameras requires a long focal length, leading to increased distance between the primary and secondary mirrors. Consequently, this results in a larger camera volume and inefficient space utilization. To decrease the launch cost and envelope size of the space camera during launch, a high-precision, repeatable secondary mirror deployment mechanism is designed based on the four-link space structure for the coaxial three-mirror optical system. The mechanism's error was analyzed, and finite element analysis was conducted to evaluate its reliability. Additionally, a repeatability test plan was devised to ensure the mechanism's consistency. Following the folding of the secondary mirror deployment mechanism, the optical axis direction length of the space camera is reduced from 875 mm to 324 mm, achieving a 63% compression in volume. In its unfolded state, the mechanism exhibits a fundamental frequency of 96.64 Hz. The maximum deviation in repeated unfolding displacement is measured at 15.61 μm, and the maximum inclination deviation is 16.89″. These results demonstrate the mechanism's effectiveness in minimizing the space camera's volume and meeting the in-orbit requirements, attributable to its locked state fundamental frequency. Furthermore, the mechanism maintains the optical system's repeatability and can accommodate the payload conditions of micro and nano satellites, making it an ideal solution for aerospace applications.