The installation method of high-voltage end bolts of high-voltage isolating switch for electric multiple units（EMU） impairs the electric field strength of the air domain in the vicinity of the bolts.In order to reduce local electric field intensity and improve the operation reliability of high-voltage insulator

it is of great importance to analyze the influences of bolt fix method on electric field distribution and select a reasonable bolt installation scheme.Consequently

we studied the optimization strategy of the bolts at high-voltage end for the high voltage isolation switch in EMU on the basis of the 3D drawing-commercial FEM co-simulation and artificial pollution flashover test.The 3D model was established to compare the variation trend of the potential and electric field distribution along the air surface or axial lines under different bolt installation methods.The effect of bolt end on the flashover discharge channel was verified by experiments in the artificial chamber.The results show that the existing bolt installation method is easy to form the discharge channel from bold end to the 1 st insulator sheath edge

the optimized bolt connection method can effectively reduce the potential gradient of the local area and reduce the possibility of forming a discharge channel on the edge of insulator sheath

the results of this study can provide references for practical engineering applications.