Abstract: The common morphological characteristics and formation reasons of coarse microstructure of automobile gears after carburizing and quenching were analyzed,and process improvement test was done to the gears with coarse microstructure.The results show that the local coarse microstructure could be eliminated through strengthening the quality control of intermediate heat processing.During the process of gear production,raw material receiving inspection should be strengthened to avoid the unqualified raw material to flow into the next working procedure.At last,the forging temperatures should be controlled strictly,especially the initial forging temperature and final forging temperature,in order to make the coarse microstructure be refined after heat treatment and ensure the quality of automobile gears.