According to the complexity of the forming process of the motorcycle tank's shell , as well as the quality issues in the punching production, finite element model was built using FASTAMP-NX software and adopting a method combining theoretical analysis with simulation technique. The deformation rules and influencing factors of the forming process for tank's top housing were simulated, and the shape of raw material, the pressure-pad-force, the friction factor and the bead resistance were acted as its main designing variables, the rules affecting its formation equality were discussed.The results show that the fractural and puckering phenomena are well eliminated process optimization. The model can improve the overall formation equality and has both theoretical and practical value.