Abstract: In this study, a new classification method is presented based on the analysis of various features of all classes of sheet-metal deformation. The pressing deformation is classified into tensile and compressive deformation according to the sense of stress and strain in the direction of absolute maximum stress. These two kinds of deformation can be illustrated by pressing strain diagram and pressing stress diagram, and there is a one to one correspondence between these two diagrams. Although, these two kinds of deformation are essentially different, but the pressing deformation of either follows an identical law, that is, the critical level of deformation, their influencing factors and measures to increase the critical level are all governed by the same laws. Thus many common laws of pressing deformation can be presented and further studied by this classification.