With the introduction of advanced foreign cars, domestic production of all kinds of gear steel so that the level of gear steel in China to a new level. Germany Cr-Mn steel, Japan CR-MO steel and United States steel SAE86 steel to meet the small module gear. Domestic truck gear United States SAE8822H steel grades, such as conical gears SAE8822H 8T, 10T bridge, the steel's chemical composition (mass fraction,%) to 0.19~0.25C,0.70~1.05Mn,0.15~0.35Si,0.35~0.75Ni,0.35~0.65Cr,0.30~0.40Mo. Literature view, hardenability control is the key to solving the problem of distortion of gears. Jominy hardenability bandwidth should be used to reduce distortion in 4HRC h steel. H steel after heat treatment of gear accuracy (contact area) 70%~80% higher than common steel, extended service life. Thus, the developed countries have provided the hardenability of carburizing alloy steel belt.