In order to comprehensively improve the structure of industrial robots stiffness, vibration frequency, reduce the structure mass so as to improve the static and dynamic performance quality of the robot overall, a robot structure optimization method based on multiobjective topology optimization was presented. In this method, first, the overall and its parts were analyzed, so as to find out its weak parts and weak positions of its main parts. Then the weak parts and weak positions of its main parts were multiobjective topologically optimized and reconstructed, thus obtained an best structure. Finally, the method was applied to an multifunctional 3kg industrial robot used on assembly and handling, which verified that the method is available and effective.