The main structure of a satellite using the traditional size method can not meet the rocket stiffness requirement, the structure stiffness optimization for the satellite were performed with the Patran/Nastran and the test. The optimized structure was analyzed and verified by the test. The results show that: 1)The mass of the optimized structure is almost unchanged, while the main structure stiffness is increased by 30%, reaching 59.87Hz, which is basically consistent with the theoretical analysis value of 57.03Hz, and meets the rocket stiffness requirement which is not less than 55.0Hz; 2) the optimized structure successfully has passed the static load examination of 2.5 times the appraisal level, and achieved the expects design value; 3) The optimized structure vibration response is basically consistent with the theoretical analysis value, and meets the requirement that the satellite structure response should be less than 20g; 4) The high stiffness and strength characteristic of satellite is achieved, has been passed the ground test and launched successfully. The process and outcome of the optimization is useful for structure design of the same type satellite in future.