The workpiece of angle steel punching machine shall be fully positioned in the fixture, and the base liquid of the workpiece shall be strictly determined relative to the origin of the machine tool, so as to meet the requirements of realizing the relative movement between the workpiece and the tool in the machine tool coordinate system. At the same time, the fixture shall also be fully positioned on the machine tool, and each positioning surface on the fixture shall have accurate coordinate dimensions relative to the origin of the machine tool, so as to meet the requirements of positioning and installation in NC machining. Because the angle steel punching machine has the characteristics of continuous multi profile automatic machining, the requirements of the fixture of the diagonal steel punching machine are higher than those of the general machine tool, which can reduce the positioning error, clamping error and deformation error in rough machining.