As an important sheet metal forming process, stretch flanging is widely applied in automobile industry. The formability of sheet metal during stretch flanging depends on appropriate process parameters. In this paper, an elastic-plastic large deformation FEM program is developed based on Mindlin shell element model. A quasi-flow corner theory of elastic-plastic finite deformation and a normally anisotropic yield criterion are introduced. Then the stretch flanging of a V-shaped sheet metal part is simulated and the effects of geometry and material on flanging are unveiled according to the calculated results. Meanwhile, a mathematical model for axisymmetric case (flanging tube) is developed based on the total strain theory and membrane assumption. Compared with material parameters, geometrical parameters exert greater effects on the formability and the flange angle is the most influential parameter affecting the free edge strain. The analytical model is easy to use, but it gives reasonable results only when the flange angle or initial flange length is small.