The invention relates to a servo system control method based on relay feedback, belonging to the technical field of motion control. The method comprises the following steps of: controlling a servo system for the first time by using a relay with an initial amplitude value to acquire a rotation rate after initial motion time; acquiring a relay amplitude value corresponding to the upper limit and the lower limit of the rotation rate according to the motion information of the first time, and respectively carrying out motion control on the servo system for the second time and the third time under the amplitude value through the relay in a time delay mode to acquire a stable response amplitude and a stable response cycle; identifying system model parameters and a dry friction magnitude according to the motion information of the second time and the third time; and carrying out optimization of control parameters and feedforward compensation of dry friction based on the identified parameters. The method of the invention can be used for quickly optimizing controller parameters and realizing effective compensation of friction, thereby improving the control accuracy of the servo system.