To study the influence of grid-side equipment on the seismic performance of the converter transformer and bushing system, finite element models of the interconnected and stand-alone ±800kV UHV converter transformer and the grid-side equipment were established The sliding of the fittings at the top of grid-side bushings was simulated. The seismic response of bushings were analyzed, and the results indicated that the frequencies of the first 20 orders of the UHV converter transformer and bushing system is close to the seismic preeminent period, thus quasi-resonance is easy to occur. The grid-side equipment can significantly amplify the stress and displacement of grid-side bushing. The relative displacement in fittings is great in earthquake. Therefore, the coupling effect between the grid-side equipment and the converter transformer should be considered.