In the process of blanking, the work hardening capability of material possesses very important significance. It not only affects the internal stress value of distorting material, the distribution of stress and the value of blanking force, but also blanking deforming limit and quality of blanked work piece. This paper carries through pure shearing fine-blanking processing experiment with negative clearance for the ASTM-Gr.D and ASTM-1022 steel as well as the micro hardness of the sheared surface for the blanked work pieces in breadthways and lengthways direction measured by Vickers-micro hardness instrument (MH-6). Mechanism of work hardening for fine-blanking with negative clearance is discussed. Meanwhile, the work hardening capability of blanked work piece is analyzed. The work hardening degree of the materials possessing different hardening index is compared. It could be concluded that the work hardening degree of the blanking work pieces was strengthened evidently by the fine-blanking with negative clearance. The hardening layer of blanking fracture could enhance structure intensity and wear resistance of blanking work piece evidently. Therefore, it could improve fatigue strength and the working life of work piece greatly.