Abstract: An approach is presented to increase scuffing load capacity of helical gears.Firstly,the flash temperature distribution on tooth is evaluated by using 3 D finite element method,mathematical programming technique and Block's equation.The calculated results show that the highest flash temperature occurs at the mesh begining and finishing corners on the tooth flank where scuffing could happen.Further,a tooth profile modification by a parabola is presented.Through the agency of optimization programming with an object function of minimizing the highest flash temperature,the optimal profile modification can be obtained.According to the numerical example,the scuffing limit load could be raised 2 5 times as unmodified helical gears.Finally,the influence of the supporting structure on the distribution of flash temperature is discussed.An optimal profile modification method is developed,which takes the deformation of supports into consideration.