The application of fracture in three-points bending to blanking of tool steel was studied. Several mechanical models of stress blanking were discussed at first. And then the experiments were made in special equipment of three points bending designed by us. Several problems, such as the effect of wedge on fracture, the effect of support condition on the quality of blanking, the effect of the geometrical parameters of notch on blanking were studied with the help of experiment. The suitable parameters of three-point bending for blanking, depth and tip radius of notch, the ratio of blanking length to the diameter of the bar and suitable support in asymmetrical geometry have been proposed.