According to the principle of friction drive of synchronous belt, synchronous belt tension is needed to work properly. In order to ensure the performance of synchronous belt, need tensioning synchronous belt to work properly again. Synchronous belt drive with a belt drive, chain drive and the advantages of gear transmission. Synchronous belt transmission due to the mesh belt and pulley transfer movement and power, there is no relative sliding between belt and pulley, can ensure the accurate transmission ratio. Synchronous belt usually use rope or glass fiber rope as stretch body, chloroprene rubber or polyurethane as matrix. The belt, thin and light, so can be used for higher speeds. Transmission with linear velocity can reach 50 m/s, transmission ratio can reach 10, efficiency can reach 98%. Transmission noise than the belt drive, chain transmission and gear transmission is small, good abrasion resistance, don't need oil lubrication, service life is longer than the friction belt. Its main drawback is that manufacturing and installation accuracy requirement is high, strict center distance. Therefore, the synchronous belt is widely used in need accurate ratio of small and medium-sized power transmission.