Abstract: The tooth stiffness was calculated by the analytical method and the finite element method. The tooth profile modification mechanism and the influence of machining errors on loadsharing ratio， transmission errors and temperature fields were analyzed by stiffness method. The results show that the long modification is superior to the short modification in reducing meshing shock. The transmission errors fluctuation is the smallest and transmission is the smoothest when long modification index equals 122. The profile modification can alter the distribution of the bulk and flash temperature， and translate the high temperature zone from tooth root and addendum to the tooth profile central. Thus the highest temperature of the tooth root and addendum reduces and the scuffing load capacity is improved. The machining error can weaken the profile modification effect and cause dynamic load and instantaneous high temperature. The machining errors， runningwear， and thermal elastic deformation should be considered when setting the amount of profile modification.

Key words: tooth profile modification, temperature fields, meshing stiffness, transmission error, loadsharing ratio