Incremental forming of sheet metal is difficult to be simulated for its complicated 3D loading path. In this work, an acceptable approach to generate 3D loading path, called “virtual guiding model method” is accomplished. The method, which has the similar idea with the conventional copy mill, is based on FEM and the basic principle of kinematics. With the help of the method, multi-stage incremental forming of a drawing typed square cup was simulated in the FEM software-PAMSTAMP and experimented. Through measuring the thickness distribution the vertical edge of the cup, the most difference between them is less than 0.05mm, which is satisfied with engineering request, and the results shows that the 3D loading path generating method is one of the most effective way to realize the incremental forming simulation.