space two-dimensional turntable is the main load-bearing structure of space photoelectric detection equipment, and collimation frame is the key support component of turntable, so its stiffness characteristics are vital for the performance of turntable. therefore, the structure of collimation frame was topologically optimized under the request of the minimum quality and stiffness maximization by using the finite element software-msc. patran/nastran. modal shape of collimation frame is regarded as the deformation of model under different incentives. the optimized results under different incentives were analyzed. considering the aforesaid optimized results and process requirements, the lightweight design result of collimation frame was obtained. the model quality after optimization is 29.42kg, and this result meet the requirements of design quality. the structure after optimized is analyzed by finite element (fea), and the result shows that the first natural frequency of collimation frame is 169hz, which satisfies the requirement of structure design. finally, the modal experiment of structure was conducted, and the results verify that the result of finite element analysis is correct.