In order to improve the dynamic response performance of CNC machine tools, the load motor inertia of the cycloid gear form grinding machine servo system was selected and designed, including theoretical calculation and rationality analysis. The feasibility and optimization plan of inertia matching was proposed, a two-mass servo drive closed-loop PID control system model was constructed, and the MATLAB simulation was carried out. The research shows that with the increase of the load motor inertia ratio, the following ability of the system gradually weakens; the feasibility of the inertia matching servo motor selection design of the forming gear grinding machine is confirmed.