The double helical gear addendum modification is achieved by using parabola instead of part of straight line on rack cutter blade.Through a predesigned parabolic function of transmission errors and combined with the equation of the rack cutter blade

the gear tooth meshing equation is derived and the gear tooth profile modification is realized.The bend-torsional coupling dynamics model of double helical gear and oscillatory differential equation of system are established.According to the double helical gear tooth contact analysis method（TCA）

the addendum modification and tooth profile modification transmission errors are obtained.Appling these errors to the kinetic equations as the error exercitation

double helical gear dynamic characteristic is studied.It is proven that tooth profile modification based on a predesigned parabolic function of transmission errors can decrease the dynamic factor of the double helical gear transmission.Thus

more effectively achieve the purpose of reducing vibration and noise.