The invention discloses a molding processing method of a roof prism, which is characterized by comprising the following steps: a. processing a prism blank into a polished square prism blank; b. respectively milling two opposite lateral edges in the square prism blank, respectively cutting a triangular prism parallelly and equivalently at two sides, obtaining a right prism blank with the bottom surface of being a hexagon after milling, wherein the hexagon has axial symmetry and the lines where the symmetrical axis are located pass through two inner angles of 90 plus or minus 5'degrees; and c. placing the right prism blank with the bottom surface of being a hexagon in a multitool cutting mold, adopting a combined cutting tool for cutting and leading the roof prism to be molded. The method has convenient operation and high production efficiency and can improve the quality of the roof prism.