The grinding allowance of large gear ring forming grinding will affect the grinding force and grinding heat,resulting in different grinding deformation,reasonable balance of allowance distribution means a lot to the quality of gear ring. Based on the grinding contact zone model,the grinding force model and the grinding and moving heat source theory,the simulation process of the deformation prediction of the ring gear grinding under the thermo-mechanical coupling is analyzed,and the optimization model of the gear grinding balance distribution is established. Taking a large gear ring as the research object,with the deformation control as the goal,the deformation of several sets of grinding gear is simulated and the optimal distribution value is obtained. The research method had some guidance significance on improving the precision of large gear ring forming grinding.