An inertia response optimization control method for a large wind turbine generator comprises the steps of 1) detecting to obtain the generator, the power grid frequency, the wind speed and the pitch angle through detection; 2) determining whether the wind turbine generator operates in a speed change stage or not, and whether the wind turbine generator enters an inertia response control mode or not; 3 ) if yes, storing the initial wind speed and the initial generator rotating speed at the moment entering into the running mode; 4 ) carrying out low-pass filtering on the wind speed; 5) calculating to obtain the optimal target control rotating speed of the generator; 6) calculating the expected generator torque output by a speed-variable control ring; 7) calculating to obtain the expected torque of the generator which is actually output; 8) outputting the expected torque of the generator to a converter of the wind turbine generator set for controlling the electromagnetic torque of the generator; and 9) determining whether to exit the inertia response control mode or not according to the power grid frequency, and if yes, recovering and tracking the expected torque of the generator to the optimal torque of the generator according to the set slope. Coordination control and smooth switching between the inertia response control ring and the speed-variable control ring are effectively achieved.