The dynamic-explicit finite element method based on the virtual power theory of the updated Lagrangian formulation was developed to analyze the flanging process of micro square cup. The forming limit, the relationship between punch load and punch stroke, the distribution of von Mises stress, effective plastic strain, and thickness were discussed and compared with experimental results for various arc radii of punches and various diameters of blanks. This study designed three sets of punch and one set of die to analyze the flanging process of micro square cup. When the diameters of blanks were identical, the punch stroke of workpiece in forming limit would increase with an increase of arc radius of punch. When the arc radius of punch was fixed, the punch stroke of workpiece in forming limit decreased with an increase of the diameter of blank. However, the punch load would decrease with an increase of arc radius of punch, when the punch stroke was fixed and the identical diameter of blank was used. When the arc radius of punch was fixed, the punch load increased with an increase of the diameter of blank. By comparison of numerical and experimental results, it showed that the dynamic-explicit finite element analysis method could be used to predict the flanging process of micro square cup reasonably.