The invention discloses a servo system inertia identification method adopting a genetic algorithm for optimization. Based on a model reference self-adaption theory, the self-adaption rule of inertia identification is designed according to a Landau discrete time recursive algorithm. The global searching capability of the genetic algorithm is utilized, a model reference self-adaption system is used as a control object, an output difference between a motor practical angular speed and an estimated angular speed is used as a control error, the integration of the product of time and an error absolute value is used as an optimization target, the self-adaption gain [beta] in the inertia identification is dynamically adjusted, and the online optimization of control parameters is realized. According to the invention, both the higher convergence speed and the higher identification precision are realized in inertia identification, and the relatively high self-adaption capability to the change of rotary inertia is achieved.