Abstract: A simplified model is proposed for the dynamic analysis of Ultra High Voltage (UHV) electrical support-equipment coupled system, based on which the dynamic properties and seismic responses of the system are investigated. Firstly, the structural characteristics of the coupled system are analyzed, and a 2E-4D model considering distributed parameters is proposed to simplify the system. A theoretical derivation is included to calculate the natural frequencies and seismic responses of the simplified model. Secondly, by analyzing two kinds of representative electrical equipment, the results obtained from the 2E-4D model are compared with the numerical simulation results for 6 different support-equipment sets, which have verified the accuracy of the simplified model. Lastly, the proposed model is adopted for parametric analysis of a large number of support-equipment systems to investigate the influence of different characteristic parameters (e.g. stiffness ratio and height ratio etc.) on the system dynamic properties and seismic responses, and the value range of dynamic amplification factor (DAF) is determined for different supporters. This research is expected to provide reference to update Chinese codes and specifications accounting for the effect of support structures on the dynamic behavior of electrical equipment.