The invention relates to a sectional material self-bending forming extrusion die, and relates to the technical field of dies. The sectional material self-bending forming extrusion die is used for solving the technical problem that the cross section deformation is easily caused when the outer side surface of a sectional material is subjected to large stress in the prior art. The sectional materialself-bending forming extrusion die comprises an upper die and a lower die connected to the upper die; and due to the fact that the area covered by an inner contour line of the upper half part of a flow guide cavity is larger than the area covered by the inner contour line of the lower half part of the flow guide cavity, and the area covered by an inner contour line of the upper half part of an extrusion cavity is larger than the area covered by the inner contour line of the lower half part of the extrusion cavity, the metal amounts flowing into the upper sides of the flow guide cavity and theextrusion cavity is more than those flowing into the lower sides correspondingly, so that a blank is pre-deformed firstly during extrusion, the extrusion load on the outer side surface of the sectional material can be reduced, and extrusion molding is facilitated.