The polygon action and the meshing impact of silent chain can be reduced by the change of the link plate structure. However, the change of the link plate structure may result in the complexity of manufacture. A new modified involute profile for sprocket is put forward based on the law of motion between the link plate and the driving sprocket. The modified involute profile is obtained by use of a unified program between VB and AutoCAD. The kinematic and dynamic simulation of silent chain with the new profile is performed by use of ADAMS. The results show that the polygon action of silent chain mechanism can be reduced and the smoothness of the silent chain drive is effectively improved as the sprocket is of the new modified involute profile.