GIS equipment has problems that the characteristics of spring contacts are difficult to quantify and the distribution of mechanical vibration is unknown. Therefore, a multi-scale equivalent modeling method via representative volume element (RVE) is proposed in this paper, which realizes electromagnetic-mechanical multi-field coupling. Based on the 550 kV GIS bus structure, a cross-scale finite element model from part scale to equipment scale is established. Through the coupling simulation of electromagnetic and mechanical mechanics, the vibration distribution principle of the shell is summarized. The results demonstrate that the error between the equivalent model and the original structure in the radial elastic response and impedance characteristics is 6.72% and 1.7% respectively, which verifies the effectiveness of the method. The vibration amplitude of the conductive rod is about 0.3 m/s2, which is 3.75 times that of the 0.08 m/s2 in the middle of the shell, and the sensor layout should focus on the energy concentration area. The research results provide equipment vibration distribution characteristics for GIS mechanical fault diagnosis and lay a foundation for monitoring network topology optimization.