The principle of an electric servo system with double pendulum nozzle of a certain type of a missile is analyzed, and the nonlinear characteristics and cross-coupling interference of two vertically-mounted electromechanical actuators are studied through the motion analysis and modeling of the system. The decoupling operation of the expansion, contraction and displacement of the actuator under random swing angle instructions of the controller is given. The nonlinear relationship between the swing arm and the nozzle swing angle is studied. Based on this, a mathematical model of a single servo mechanism with nonlinear links is established, and the controller parameters are adjusted. The time-domain based step response method and the frequency-domain based sinusoidal correlation analysis method are used, and a simulation is carried out on the Simulink platform. The result is compared with the real experimental data, which verifies the accuracy of the model and lays a solid foundation for further research on the performance test of this type of servo mechanism.