The invention belongs to the field of construction materials and relates to exterior wall putty. The exterior wall putty comprises the following components by weight: 10-15 parts of polymer powder, 30-50 parts of light clay bricks, 10-15 parts of perlites, 6-9 parts of high-alumina cement, 12-18 parts o mullites, 10-15 parts of bentonite, 2-4 parts of szaibelyites, 1-3 parts of dextrin powder, 3-5 parts of methyl cellulose, 5-8 parts of silica powder, 5-10 parts of fibrilia or viscose, 8-18 parts of water glass, 4-6 parts of dispersable emulsion powder and 10-15 parts of aluminium oxide solutions and silicon dioxide sol composite suspension solutions combined at the mass ratio of 1:1; the polymer powder is a modified mixture of polyethylene and polypropylene; the specific modification comprises the following steps by weight: 4-9 parts of aluminium dihydrogen phosphate, 0.5-4 parts of C12H25SO3Na, 3-4 parts of EPDM, 6-8 parts of aluminium acid ester coupling agents and 2-3 parts of phosphate ester are added into a base material which consists of 30-60 parts of ultrahigh molecular weight polyethylene with the molecular weights of 4-7 million and 15-25 parts of high density polypropylene with the molecular weights of 1-1.4 million; the mixture is kneaded in an internal mixer for 40-50 min at the temperature of 110-120 DEG C. according to the invention, the exterior wall putty is excellent in adhesiveness and filling ability and can prevent walls from discoloring and falling off.