Three-dimension rigid-plastic finite element software, DEFORM-3D, was used to simulate the integral forming processing of a lager thick-wall semi-sphere head with supporting tables. Influencing factors of integral forming, such as initial blank shape, radius of corner at the bottom of the protrusions and the preforming mode etc, were researched quantitatively. A double layer frustum cone blank was determined, which can reduce the variable amplitude of the wall thickness and cause a uniform wall thickness distribution. When radius of corner at the bottom of the protrusions of the machined blank was in 100~130mm, no crack occurred at the bottom of the any supporting tables and a rational size can be obtained after forming. Using mode C (two banding protrusions) to forging the blank for machining can prevent the center metal from thinning and reduce additional tensile stress. Based on the simulation research, the 1:3 scale experiment was done in 31.5MN hydraulic press and the test piece was measured. The result shows that the error between simulation data and test data is less than 5%, which verified the feasibility of integral forming and provided an important reference for virtual production.