This paper presents a fuzzy controller design for a drive system of lower limbs rehabilitative robot. In this system, turning the design of the fuzzy controller into an optimization of the parameters, using genetic algorithm to make an optimizing design of the fuzzy controller could get rid of the reliance on the experience knowledge and the cut and try method in the design of the fuzzy controller years before. By the theory of analyzing and the simulation experiments, we can conclude that, in the robots' drive system, using fuzzy controller to instead of PID controller could get better control effect, also improve the dynamic performance, especially on rapidity and robustness.