Abstract: The SA-240M 304 stainless steel dished closure head was manufactured by submerged arc welding. A simple finite element model was established to simulate the Mises equivalent stress field of dished closure head under rigid bias constraint working condition. The results show that the Mises equivalent stress in the middle of the circular circle on the right side of the elongated hole of the dish closure head was the maximum, which was the dangerous area. The relative error between simulation value and the stress calculated from the measured strain was only 4.7%, which verified the accuracy of the model. After equivalent linearization of the normal stress along the stress classification line in the dangerous area, the primary film stress, primary bending stress, peak stress and secondary bending stress were obtained, which were 135.19, 3.54, 0.774, 42.83 MPa, respectively, and were rated as safe according to ASME VIII-2.