Die forging for cylinder end is a complicated process with large deformation. It is hard to analyze the forming process by using the analytical method for many factors which affect the forming quality . The whole forming process was simulated by numerical simulation method ，and the metal flow behaviour of the clylinder end forming was obtained. At the same time, some defeats such as unfilled and folding in forming process were analyzed，and the dimension parameters of the preform shapes needed to be amended were pointed out. The experimental results show that the satisfied final forging can be obtained by using the revision dimensions of the preform shapes.