Abstract: In this paper, based on the gear theoretical model, the grinding results on the gear profile grinding machine are simulated according to the carburizing and quenching heat treatment deformation, and the type modeling is conducted. The root bending stress is analyzed by using the UG NX12 finite element analysis to find out the differences and rules, then they are compared with the relevant provisions and formulas in the national standards, and a kind of virtual tooth root arc is established. The model and theory of tooth root circular arc and grinding circular arc of synthetic gear are derived tentatively from the difference between the stress correction coefficient of gear with grinding step in the standard, the corresponding relationship between tooth root circular arc and stress is found out, and the method of reducing the tooth root stress is also given.