In this paper

the factors influencing the mechanical endurance of vacuum interrupter（VI）

such as optimization of the structure

design and manufacture technology of bellows

fixing methods of shielding tube

and assembling technology of VI etc.are analyzed.The bellows is improved in several aspects

the structure

material

manufacturing technology

external treatment

and welding method.Besides

the defects in VI design are also advanced.The results are used in TD14A-12/1600-31.5C vacuum interrupter

and the VI has passed 100000 times mechanical endurance test successfully.