Based on the analyses of the structural feature and the function requirements of newstyle bottle cap, the two fundamental components, the 1ining washer and the outer body, are abstracted as a plate and a cylinder with thin wal1 respectively. For simulating the deformation of the 1ining washer under equiaxia1 pressure, the modified Lagrangian finite element analysis is applied on the 228 triangular elements. Under assembly pressure, the plastoelastic deformation of both the 1ining washer and the outer body are studied in terms of Tresca’s yield criterion and the limitation of the plastic deformation is presented when the two components are assembled into one unit. For the production of this kind of bottle cover, experiments are carried out by carefully measuring the changes of the diameter of 1ining washer as well as that of the outer body. It is shown that results from the experiments have a good agreement with the theoretical calculation and the maximum value of the allowable pressure has successfully been used in the design of newly developed bottle cap production system.