Abstract: According to authors’ research results of the scuffing theory for gears, the third theoretical calculation system of gears----the new methods for calculating the scuffing strength of gears, is first established. Three calculation formulae for check, dosing as well as contrast re presented respectively. Because some calculation results have been used and verified for several years in practice, the reliability of study could be comfirmed.

Key words: Design, Gear, Scuffing