The complex and harsh thermal environment of low-orbit satellites necessitates strict requirements for the performance of the optical-mechanical structure of remote sensing cameras. In this study, an integrated opto-mechanical-thermal simulation analysis method based on an on-orbit temperature field is proposed by using a low-orbit satellite camera as an example. Thermal desktop, MSC Patran/Nastran, and Code V are used to construct the thermal, structural finite element, and optical analysis models, respectively. The structural deformation characteristics, including the shift, tilt, and distance of each mirror in the most extreme conditions of single camera imaging time, are obtained. Changes in the MTF of the optical system are analyzed and the primary influencing factors of the system transfer function are determined. Subsequently, optimization design is performed based on the structural parameters of the primary force-taking structure. The optimization results show that the thermal characteristics of the system are optimal when the linear expansion coefficient of the primary force-taking structure ranges from 5.0e-6 to 5.5e-6, and the system transfer function meets the target requirements.