To reduce the effects of gravity deformation on the imaging quality of large aperture ground-based telescopes during optical tracking， a parallel adjustment mechanism with high lateral stiffness and submicron accuracy based on flexible hinges is developed. First， a system of parallel mechanism is introduced and a two-degree-of-freedom flexible hinge is designed according to specific technical indicators. Second， equivalent kinematics and stiffness models of the flexible hinge parallel mechanism are developed. Subsequently， a rigid-flexible coupling kinematics simulation system of the parallel mechanism is established， and the effects of the flexible hinge on the accuracy of the mechanism are analyzed. Finally， an experimental test system is built to verify the rationality of the flexible hinge design and the accuracy of the rigid-flexible coupling kinematics analysis of the parallel adjustment platform. Simulation and test results show that the rotational stiffness error of the flexible hinge is controlled to within 3.54%， the motion accuracy of the small displacement （micrometer/angular second） reaches the sub-micrometer level， and the motion accuracy of the large displacement （millimeter/degree） is controlled to within the micrometer level as compared with the simulation results. The lateral stiffness of the mechanism is greater than 60 N/μm and can thus meet the requirements of ground-based telescope optical imaging.