The gas insulated switch (GIS) vibrates during operation. In order to analyze the difference between the vibration signals for loosed bolts or misaligned conducting rods at the connection of GIS shell and the normal operation without defects,a 3D model of 252 kV three-phase box-type GIS is established in this paper. Computational modal analysis is firstly performed on the model in the field of solid mechanics. Secondly,the natural frequency is determined,and the representative sixth mode shapes are obtained. By applying different loads and changing the parameters of the model,the time-domain signals of the vibration acceleration of GIS shell under the state of no fault,different number of bolts loose and different cases of conducting rod misalignment are solved in the solid mechanics field. Then the frequency-domain signals are obtained through spectrum analysis. By comparing and analyzing the difference of vibration acceleration signals of GIS shell in several cases,the characteristics of vibration acceleration of GIS shell in case of bolt loosening fault and conducting rod misalignment fault are obtained. Finally,the criteria for the above faults are obtained. Some certain reference value about the follow-up GIS equipment running condition monitoring,mechanical fault identification and vibration research have been provided in the conclusion of this paper.