Four-node quadrilateral plate element PLANE182 is taken as a reference element to conduct the finite element calculation for spherical sealing structure widely used in rocket engine propulsion system pipeline. The function expressions of stress field, strain field and displacement field of tube connector were obtained. The sealing mechanism of tube connector is analyzed. The importance of elastic-plastic deformation to metal sealing is discussed. Based on the above research, the elasto-plastic and contact analyses for the contact element and coupled contact analysis for the tube connector are conducted by means of non-linear finite element method. The mechanical property testing of coupled contact bodies was carried on ANSYS platform to determine the displacement, strain and stress distribution of the tube connector.