Abstract: When the foot-end trajectory planning of the legged-robot is carried out in the task space, the nonlinear mapping relationship between the task space and the joint space will cause the speed and acceleration of the joint motor to exceed the limit or mutate, thus affecting the motion stability of the robot. In order to solve this problem, a trajectory generation algorithm of legged- robot based on optimal time interval is proposed in this paper. Firstly, a series of discrete points of the foot-end trajectory are planned in the task space, and the corresponding joint angles are calculated by using the inverse kinematics solution. Secondly, the joint angles are taken as constraints, and the time interval between the trajectory points is taken as the optimization object. The functional relationship between the robot joint speed, acceleration, acceleration speed and time interval is established, and a multi-objective optimization model oriented to the optimal time interval is constructed. Finally, egmented chromosome segment mutation are introduced to improve the traditional genetic algorithm to obtain the optimal solution of robot motion performance. The comparative experiments show that the peak acceleration in joint space is reduced by 73.58%, the peak jerk is reduced by 77.15%, and the acceleration in Y-direction is reduced by 61.82% in task space.