The problems of the two-axis fast steering mirror based on flexible support was put forward firstly, a servo mechanism structure of the two-axis fast steering mirror based on flexible support was introduced briefly, the pulse transfer function of the servo mechanism was established, the MIMO system parameter identification theory was discussed, and the method based on COR-IV method was analyzed. Based on the method, the identification method of servo mechanism based on flexible support for the two-axis fast steering mirror was proposed and simulated. The experiment for the identification of servo mechanism parameters was designed to verify the method and the experimental results were compared with theoretical calculations. The experimental results show that the MIMO system parameter identification algorithm based on the COR-IV method is effective, the identification accuracy is within the expected range, and the identification results can provide data support for the adaptive control of fast steering mirror.