Chain drive is a transmission mode which transfers the motion and power of the driving sprocket with special tooth form to the driven sprocket with special tooth form through the chain. Chain drive has many advantages. Compared with belt drive, it doesn's have inelastic sliding and sliding phenomenon, having accurate average transmission ratio, reliable operation and high efficiency, large transfer power, strong overload capacity and small transmission size of under the same working condition. The required tension force is small, and the pressure on the axis is small. It can work in high temperature, humidity, dust, pollution and other harsh environment. The disadvantages of chain drive mainly include: it can only be used for transmission between two parallel shafts, high cost, easy wear and elongation, poor transmission stability, additional dynamic load, vibration, impact and noise generated during operation. It should not be used in rapid reverse transmission. The advantages include: large transmission power and high transmission efficiency.