Many factors need to be considered in the analysis of gear system dynamics. Mesh stiffness and error excitation make the most infection in the system. As a periodically variational excitation that exist in the mesh gears

error excitation is one of the primary factor that causes the vibration of gear system

error excitation is analysed and calculated. The synthetical principle and evaluate process of short-period errors of a gear pair in the gear system is given

considered about total contact ratio and the randomicity of gear errors. In the end

a calculation example is given

the result shows that the method is the validity.