The invention provides a composite low-phosphorus corrosion and scale inhibitor and application thereof. The composite low-phosphorus corrosion and scale inhibitor is prepared from a corrosion and scale inhibitor A and a corrosion and scale inhibitor B, wherein the corrosion and scale inhibitor A is prepared from 20-40 parts of polyepoxysuccinic acid (PESA), 20-40 parts of sodium gluconate and 20-60 parts of water; and the corrosion and scale inhibitor B is prepared from 10-25 parts of hydroxypropyl methacrylate (HPMA), 10-25 parts of acrylic acid / 2-acrylamido-2-methylacrylsulfonic acid copolymer (AA / AMPS), 5-10 parts of 2-phosphonobutyl-1,2,4-tricarboxylic acid (PBTCA), 10-25 parts of zinc salt, 1-2 parts of fluorescent tracer and 13-64 parts of water. The technical scheme is as follows: the corrosion and scale inhibitor A and the corrosion and scale inhibitor B in a weight ratio of 1:2 are compounded with water. The composite low-phosphorus corrosion and scale inhibitor has excellent corrosion and scale inhibition effects, and thus, the phosphorus content in the product is low, thereby reducing the phosphorus discharge and having favorable environmental protection performance.