Abstract: The process of double compression connection of the DN40 light-walled stainless steel pipe is completely simulated by means of finite element (FE) model,and the deformation process,and stress and strain state of the pipe joint,the O-ring and stainless steel pipe proper are analyzed. Based on the contact stress distribution regularity of the O-ring,the improved multi index evaluation method for the sealing performance of the clamping connection is adopted,and the sealing performance of the clamping connection is analyzed by combining the minimum contact stress and the sealing strength,which improves the safety and reliability of the sealing structure. Meanwhile,explored are the regularities of the influences on the sealing performance of the compression connection by such factors as the sealing groove angle of the pipe joint,the inner diameter of the calipers groove and the hexagonal width of the jaw. The research result has important reference significance for the optimal design of the stainless steel pipe fitting joint and the caliper.