To evaluate the seismic performance of a porcelain bushing for 1 100 kV ultra-high voltage (UHV) gas-insulated switchgear (GIS), the porcelain bushing with its supporting stand and canister were installed on a shaking table platform, and a shaking table test was carried out on the UHV GIS porcelain bushing. In the shaking table test, an artificial wave that conforms to the UHV standard response spectrum was used to excite the porcelain bushing. The dynamic characteristics of the porcelain bushing, the acceleration and displacement response of the bushing top, and the strain response of the bushing root were obtained. The numerical simulation on the shaking table test was performed using the simulation software ABAQUS, and then the natural vibration frequency of the model, the stress of the bushing root, and the relative displacement of the bushing top were obtained. The values are well consistent with the test results, which proves the efficiency of the numerical model. The influence of the natural frequency of the bushing and stiffness of the body (support cylinder and bracket) on the seismic performance of the bushing were studied by numerical simulation. The results show that the seismic response of the bushing is relatively small when the natural frequency changes within a certain range. The maximum stress of bushing root and maximum relative displacement of bushing top decrease with increase of body stiffness; therefore, the seismic response of the bushing can be reduced through the increase of body stiffness.