For the problem of the low efficiency of robot under a certain working environment,a trajectory planning method based on optimal time is put forward. Firstly,by using the seven times B spline curve,the interpolation of the robot position time series is completed. Then the kinematic constraints are transformed into the constraints of B spline control vertex. Finally,the time optimal trajectory meeting the kinematics constraints and torque smoothing is obtained by using genetic algorithm,based on the optimization target of robot joint trajectory optimal running time. The experimental results show that the cumulative effect of the planning algorithm could obviously be reduce the jerk and the optimal time of the robot performing trajectory is improved.