The invention discloses a method for automatically adjusting speed loop control parameters of an alternating-current servo system based on inertia identification, which comprises the following steps: firstly, a current loop and a servo motor are used as generalized objects, and estimated values of the servo motor and the rotary inertia loaded on the servo motor are obtained by the inertia identification based on a disturbance torque observer; and then a pole collocation method is adopted to adjust proportion parameters and integral parameters of a speed loop proportion integration differentiation (PID) controller automatically. In method for automatically adjusting the speed loop control parameters of the alternating-current servo system based on inertia identification provided by the invention, by combining the inertia identification algorithm based on the disturbance torque observer with the characteristics of an alternating-current servo system, auto-adjustment of the speed loop PID parameters for the alternating-current servo system can be realized under different rotary inertias. Engineers do not need to set and adjust the controller parameters manually according to the experience and the system can automatically carry out the auto-adjustment of the speed loop parameters. Compared with the prior art, the method for automatically adjusting the speed loop control parametersof the alternating-current servo system based on inertia identification is simple in design principle, and has the advantages of good adaptability under the condition that the inertia change of the external load equipment is obvious, and the like.