The synchronous belt has been applied widely in mechanical power and movement transmission.However

because of polygon effect between synchronous belt and pulley

the accuracy of transmission is reduced.A model of transmission error are established by tooth profile parameters of new design’s synchronous belt and pulley.Several previous designs are compared with the new designs.Analyses suggested that errors in the linear displacement of the belt

angular velocity of driven pulley

and the fluctuations of belt speed are attributed to the structural parameters（tooth profiles） of the synchronous belt and pulley

which result in reduced precision of transmission.The results prove that precision of the new type synchronous belt transmission is higher.