Based on the analysis of S curve control method,aiming at the robot acceleration and deceleration time is too long and severe vibration in the process of start,stop,resulting in the motion precision problem of robot,a 5 order S curve with time optimal and the smallest impact is proposed. Under the premise that ensure the robot motion constant,with the least amount of acceleration and deceleration time and smooth movement as the optimization index,the improvement of 5 order S curve design is carried out. Finally,the simulation verification of improved S curve is carried out,the simulation results show that,for the conventional 5 order curve,the optimized 5 order S curve acceleration and deceleration time is shortened,and the acceleration curve is more smooth.