Abstract: In this paper, establishing a model of the 330kV GIS substation shell in transient state, a simulation calculation generated about Transient enclosure voltage(TEV) during switching of disconnector, and the TEV waveforms and spectral distributions were obtained throughout the casing. The simulation results are compared with the actual experimental data of the substation, and on the basis of verifying the correctness of the simulation calculation, the possible hazards caused by transient elevation of ground potential are analyzed. The study shows that the maximum value of TEV always appears on the casing of the casing, which can reach tens of volts and contain complex frequency. At the same time, the transient potential difference between the grounding lead and the grounding terminal of the main control room is close to 1000V.