Gear noise is the main part of mechanical transmission noise. There are many factors influencing gear noise, and gear accuracy will exert very important role on forming gear noise. A big noise was created from the second follower gear during transmission testing. Cumulative pitch error was found to be out-of-tolerance extremely after detecting metallurgical structure and distortion. Moreover, gear contact accuracy is low .Gear distortion was controlled by adjusting the parameters of carburizing and quenching and improving loading mode of gear furnace charge. Meanwhile, contact accuracy and the gear life were also improved.