For improving the control stability and productivity of hexapod robot's leg, the quintic B-spline trajectory planning strategy in the joint space was presented. The velocity, acceleration and jerk trajectory is continuous. According to the convex feature of B-spline, the joint constraints on velocity and acceleration was transformed to the control points of B-spline. Time optimal trajectory was planned together by the genetic algorithm toolbox of MATLAB. The penalty function was used to deal with the joint constraints . The simulation results show that the proposed trajectory planning method is effective and feasible.