In this paper, the seismic performance of polymeric-housed electrical equipment and the vibration absorption effect of dampers are investigated. To this end, a shaking table test was carried out on a polymeric-housed UHVAC capacitor voltage transformer, and the dynamic characteristics and seismic response of the equipment was analyzed throughout. White noise test results show that the first-order frequency of the equipment slightly reduced from 1.07 to 1.04 Hz after the dampers were mounted, which means that the damping device had a slight influence on the overall stiffness of the structure. The maximum stress and displacement response of the original structure under the input of artificial seismic waves with a peak ground motion acceleration of 0.2g (PAG=0.2g) were 46.33 MPa and 349.12 mm, respectively. The maximum stress and displacement response of a structure with PAG=0.5g after damper installation were 27.64 MPa and 330.06 mm, respectively. Based on simplified equivalent analysis, the reduction rates of the maximum stress and displacement are respectively 62.34% and 49.33% when PAG=0.3g, and 76.14% and 62.18% when PAG=0.5g. This shows that the seismic performance of equipment greatly improves after damper installation. This research can provide parameter data for seismic performance analysis of composite electrical equipment and the application of damper devices.