The enterprise applies multipass flanging process to manufacture large-diameter T-tube now. The pre-manufactured hole of tube was designed according to pressing deformation law, which could manufacture equal diameter T-tube through once flanging. Meanwhile the flanging process was simulated by Deform software. Then the pre-manufactured hole of large-diameter tube and movement velocity of punch were optimized by using Artifical Neural Network combined with Genetic Algorithms，through which T-tube with better forming quality could be obtained. Finally, through researching multipass flanging process of large-diameter T-tube, the conclusion was obtained as follows:tube of pre-manufactured hole which is based on pressing deformation law can once form T-tube of specific altitudes,but the flanging process parameters shall be optimized.