The invention discloses an acid rain-resistant antifouling aqueous nanometer polyurethane exterior wall finish. The finish is obtained by mixing a primary finish, a curing agent and water according to a weight ratio of 10:1:1, wherein the primary comprises water, a dispersant, a wetting agent, a defoamer, propylene glycol, rutile titanium dioxide, a nanomaterial with the particle size of equal to or less than 20nm, a chemical inert filler, an antiseptic, a mildew inhibitor, a pH conditioning agent, a film forming assistant, an aqueous polyurethane resin containing -OH, and a thickening agent; and the curing agent comprises polyisocyanate containing -NCO, and PMA (polymethyl acrylate). The exterior wall finish of the invention has the advantages of acid rain resistance and good antifouling performance.