Abstract: In order to lightweight design a new energy main reducer assembly, we have adopted a new process route for the main reducer gear, that is, hobbing → carburizing quenching → induction annealing of the inner hole → fine inner hole → laser welding（and differential shell） → main reducer teeth. In this paper, the local induction annealing process of the inner hole of the product was studied, and the magnetic thermal coupling numerical simulation calculation was carried out by COMSOL finite element software, and the comparison and analysis were made with the test results, providing a new simple, efficient and reliable process model estimation method.