Abstract: The cracking cause of inner cavity of pulsation vacuum sterilizer was analyzed by means of physical and chemical inspection,macroscopically and microscopically examination. The residual stress,which arises from welding of stiffener during manufacturing of the pulsation vacuum sterilizer,damages the passivity film. There was trace Cl- in high temperature steam. Therefore,the stainless steel of inner cavity will be so corroded under the action of both residual stress and Cl-. Some feasible suggestions on preventing the inner cavity of pulsation vacuum sterilizer from being stress corroded and cracking were offered.