collimation frame is the key supporting component of space two-dimensional turntable. its stiffness characteristics are vital for the performance of turntable. in order to reduce weight and improve rigidity, a lightweight collimation frame is designed. compared with some commonly used aerospace materials, titanium alloy is chosen as the material of collimation frame for its excellent advantages. modal analysis of the collimation frame is realized by using finite element analysis software msc. patran/nastran to verify whether the stiffness of frame meet the design requirements. the results of analysis show that the first natural frequency of collimation frame is 169.5hz, which satisfies the design requirement of stiffness. then, modal experiment is conducted to verify the correctness of the results obtained from finite element modal analysis. the results of experiment show that simulation and experiment results agree well, which further confirm the correctness of the finite element modal analysis. therefore, it proves that the selection of material and the design of structure are feasible. © 2017 spie.