The tracking servo system of an optoelectronic theodolite is studied based on the momentum moment theorem and Euler dynamic equation. The mathematical relationship and the nonlinear biaxial coupling dynamic model of gimbal system are derived by analysis and research of the coupling action of inertia moment

velocity and dynamics of axes in gimbal system. Then a electromechanical dynamic model for describing the dynamic characteristics of tracking servosystem is established according to the torque motor equation of execute component and is verified by comparison of testing method and computer simulation respectively. The model can set up a foundation for the further simulation and experimental research and can provide theoretical references for the design and simulation verification of the tracking servosystem of optoelectronic theodolite.