In the interpolation process，the precision and the speed of acceleration/deceleration contro1 is an important target of the CNC system，which determined the performance of CNC system .In the CNC device, in order to ensure the machine that did not generate an impact, out-of-step, super-way or oscillation，it must control acceleration and deceleration to feed motor pulse frequency or voltage，when it started or stopped .It analysesd mainly the linear and the S-curve acceleration/deceleration control methods under the assigned pulse control mode. The computer simulation shows that the linear acceleration and deceleration method is simple, but the existence of the impact; S-shaped curve and composite curve acceleration and deceleration law is no impact, moderate speed, but the computational complexity. Therefore, depending on the control precision and control to choose the right speed acceleration and deceleration control method is very important.