Abstract: In view of the phenomenon of scrap of a low carbon alloy steel gear due to large distortion of gear plane after carburizing and quenching, the influence factors such as heat treatment tooling, blank raw materials and normalizing process were analyzed through deformation detection. The results show that unqualified normalizing pretreatment is an important cause of gear deformation. The isothermal normalizing pretreatment plays an important role in preventing the deformation of gear during heat treatment.