Abstract: Based on the 3D rigid body motion model, a six-degree-of-freedom motion equation of three-dimensional vibration isolation system is constructed, the conditions for the dynamic decoupling of the six-degree-of-freedom are proposed, the vibration eigenvalues of the translational and swing modes are solved, the translational and swing response transfer functions of the flat-pendulum coupling vibration response are derived, and the influence of different system parameters on the dynamic response of the three-dimensional vibration isolation system is systematically studied. It is found that the three-dimensional vibration isolation system designed based on the principle of consistent vertical deformation can realize partial dynamic decoupling. The key influencing parameters of the swing-pendulum coupling vibration response are the vertical frequency, the vertical eccentricity ratio of the superstructure, the horizontal vertical stiffness ratio and the damping ratio of the vibration isolation system, and the swing response is also affected by the bottom width. Based on the theoretical formulas of translational relative displacement transfer ratio, translational acceleration transfer ratio and oscillating displacement effect ratio, it is suggested that when the vertical eccentricity ratio is less than 1.0, the vertical frequency should be 1.0 Hz-3.0 Hz, when the vertical eccentricity ratio is 3.0-6.0, the optimal vertical frequency should be 3.0 Hz-5.0 Hz, and when the vertical eccentricity ratio exceeds 6.0, the vertical frequency should be 5.0 Hz-10.0 Hz. For the three-dimensional vibration isolation system with a vertical vibration isolation frequency of 3.0 Hz, it is recommended that the parameters of the vibration isolation system be not more than 0.1 in the horizontal vertical stiffness ratio, not more than 3.0 in the vertical eccentricity ratio, not less than 0.2 in the horizontal damping ratio, and not less than 0.15 in the vertical damping ratio.