The method for the mesh stiffness calculation of gear pair through Loaded Tooth Contact Analysis is presented in this paper. The mesh stiffness and load distribution of a helical gear pair are calculated. On that basis, the effect of two kinds of axial angle errors on mesh stiffness is compared and the effect of axial modification on mesh stiffness is analysed. The research demonstrates that the axial angle error has a big influence on load distribution on tooth surface and mesh stiffness of gear pair, axial modification improves the meshing quality and load distribution.