In basic sheet metal forming process such as cylindrical deep drawing, bulging, hole flanging (or reaming), etc., deformations in-plane can be considered as changes of the curvature of different microrings. The deformation of each microring is equivalent to a bending process of plate with small width. The differential balance equation of the deformation region can be expressed as simple form of unification. The deformations in the symmetry plane of the sheet metal are part of bending and reverse bending, so the bending analysis method can be used to analyze operation. Some results were obtained by the bending analysis method.