The tooth profile modification can generally choose straight line modification and parabolic modification.Different modification curves have different modification parameters.In order to accurately determine the best modification curves and modification parameters of this curve

basing on analysis of the vibration that effected by transmission error

a pair of gears with parabolic modification meshing process is simulated with FEM approach.Aiming at reducing the fluctuation of transmission error

optimum profile modifications of spur gears is designed by genetic algorithms.The research shows that the approach is accurate and efficient to choose the best curve and fix the profile modifications of spur gears.It can also avoid impact of meshing and reduce the fluctuation of transmission error.The approach illustrated in this paper provides a new way for designing the noiseless gears.