The invention discloses a circulating water phosphorus-free corrosion and scale inhibitor and a preparation method thereof, and belongs to the technical field of water treatment agent preparation. Thecorrosion and scale inhibitor comprises the following components in parts by weight: 10-20 parts of polyepoxysuccinic acid or polyaspartic acid, 10-35 parts of sodium gluconate, 10-20 parts of acrylic acid-2-acrylamide-2-methyl propane sulfonic acid copolymer, 5-10 parts of zinc salt, 3-15 parts of molybdate, 1-3 parts of a copper corrosion inhibitor, 1-2 parts of a fluorescent tracer, 1-2 partsof a pH regulator, 5-10 parts of isothiazolinone and the balance of water. The phosphorus-free corrosion and scale inhibitor has the advantages of high corrosion inhibition rate, high scale inhibitionrate, low cost, no phosphorus, wide scale inhibition spectrum, wide pH application range, sterilization and slime stripping effects, low toxicity, chloride resistance, simple operation, controllablecirculating water agent concentration, safety and high efficiency, and belongs to an environment-friendly corrosion and scale inhibitor.