The invention relates to a compound corrosion and scale inhibitor which comprises the following raw materials according to mass ratio: 15%-30% of organic phosphonic acid, 10%-20% of acrylic acid or acrylic acid copolymer, 2%-10% of poly-maleic acid, 1%-3% of azole ramifications, 15%-30% of multivariate organic sulfonate, 2%-6% of dimethyl formamide and 20%-35% of water. The compound corrosion andscale inhibitor of the invention is used for a system which employs normal water as circulating cooling water, so as to solve corrosion problem caused by circulating water of normal-water to equipment. Corrosion rate of copper product is lower than the national standard of 0.005mm/a, thereby generating no equipment scaling caused by calcium phosphate deposition. Compared with corrosion inhibitorsof the same kind, the compound corrosion and scale inhibitor has a lower dosage and is effective in corrosion and scale inhibiting. The compound corrosion and scale inhibitor is simple in operation, convenient, quick, safe and efficient.