The function of the elevator is to help a lunar rover arrive at lunar surface from the top of a lander after landing. So the performance of it determines that whether lunar rover can arrive at the lunar surface successfully. Different compress extent of the lander leg and complicated condition of landing location make elevator design more difficult. The movement rule of rocker-arm style elevator was found after synthesizing the requirement on all kinds of unloading conditions, and the elevator was designed to meet the rule. Experiment results show that it meets the requirement of the lunar rover unloading and has higher lunar surface adaptability.