Following the increase in the aperture of space optical telescopes, the inconsistency in space and ground mechanical environment results in serious degradation of the system image quality in orbit. Gravity needs to be compensated during the alignment and test procedure of a space telescope. However, quantitative analysis and optimization methods for unloading the point coordinate have not been completely developed. First, the deformation mechanism of a large-aperture telescope under 1g gravity was studied. According to the separate closed-loop location and closed-loop mass, a mathematical algorithm was developed to optimize the position of the unloading points. By performing co-simulation, we were able to optimize the coordinates. Subsequently, simulation experiments were performed to verify the actual effect of the telescope model under different unloading parameters. The closed-loop location analysis method improves the displacement of the highly sensitive optical components from 370 μm, 36″ to 72.9 μm, 0.3″. The maximum relative deviation of the closed-loop mass method from the set value is approximately 74%. The closed-loop location gravity-compensation method can achieve a value closer to 0 g. However, its error sensitivity is high, and realizing the engineering results is difficult. The total unloading rate is approximately 75% based on the closed-loop mass gravity-compensation model, and the sensitivity is low. This model can satisfy the demand for mechanical environment of semi-physical simulation experiments using gravity unloading.