In order to solve the problem that it is difficult to fully consider the dynamic characteristics （amplitude-phase frequency characteristics） requirements in the PID parameter design of electromechanical servo system， a PID design method for dynamic characteristics is proposed. The 9-order Transfer Function （TF） model of electromechanical servo system is established based on dynamic equation. The relationship between Routh criterion and TF coefficient is used to supplement the stability constraint of the system and the compatibility constraint of TF coefficient to ensure the stability of the system and the compatibility of TF coefficient in the PID design process. On this basis， based on the idea of parameter identification， the rational fraction orthogonal polynomial method is used to identify the coefficients in the TF model， so that the PID parameters are quickly determined， which improving the design efficiency， and multiple groups of controller parameters that meet the original index can be identified by adjusting the in? dex data. The simulation results show that the designed PID parameters not only meet the requirements of dynamic characteristics， but also take into account the compatibility of system stability and TF coefficient. The design results are in good agreement with the simulation experiments.