In the process of applying cold-stretching process to normal pressure vessel, the vessel will undergo two stages of elastic and plastic deformations. If the plastic deformation occurs, the minor change of deformation in the vessel is sensitive to the pressure. Therefore, the reasonable control of the deformation in the vessel is one of the key steps in the cold-stretching process. The resistance strain gauges（RSG） were pasted in the main parts of the vessel to determine the relationship between the elastic deformation of the corresponding position and the cold-stretching pressure applied gradually. In addition, the verification of the reliability of the finite element（FE） analysis was carried out based on strain measuring results. In the plastic deformation stage, the FE was used to analyze the overall deformation law of cylinder, head and around the nozzle of the vessel under the cold-stretching pressure, meanwhile the position where the maximum deformation occurred in each part of the vessel was obtained. The results show that the local maximum deformation of the vessel is 8.24%, which appears inside of the nozzle root, and meets the requirement of local maximum deformation of no more than 10% in the current standards.