The invention discloses a radiator mainboard trimming and flanging forming mold. The mold comprises an upper mold and a lower mold; the upper mold includes an upper mold base, a flanging concave mold and a trimming convex mold; the trimming convex mold is arranged at the bottom of the upper mold base; the flanging concave mold is arranged in the trimming convex mold; the lower mold includes a lower mold base, a flanging convex mold fitting the flanging concave mold, and a trimming concave mold fitting the trimming convex mold; the flanging convex mold is aligned to the flanging concave mold, and is fixed on the lower mold base; and the trimming concave mold is aligned to the trimming convex mold, coats the flanging convex mold, and is fixed on the lower mold base. A trimming procedure and a flanging procedure of a radiator mainboard are combined to perform, so that the production efficiency is improved, the error caused by repeated positioning of the mainboard is reduced, the error caused by the strain effect and the like in the forming process of the metal mainboard is reduced, and the product precision is improved.