The invention discloses a hinge structure of forming blocks for a plastic extrusion forming die. A lower forming block and an upper forming block are provided with a hinge matching structure; the hinge matching structure is arranged at edge positions close to the side faces of the lower forming block and the upper forming block; and the hinge matching structure is characterized in that: a cylindrical bulge hinged shaft structure facing the lower forming block is arranged on the upper forming block; the axis of a cylinder is parallel to the side faces of the lower forming block and the upper forming block; and a concave structure matched with the bulge hinged shaft structure is arranged on the lower forming block. By adopting the technical scheme, the global stability of the forming blocksin the process of producing products is ensured, parison subjected to dry forming is further formed, the overall forming effect of the whole forming block is enhanced and deformation internal stress of the forming blocks is eliminated so as to obtain the products meeting quality standard. The hinge structure is convenient to assemble and disassemble, reduces processing time and saves processing cost.