The invention relates to a scale and corrosion inhibitor for circulating cooling water. The inhibitor comprises components of, by weight: 15% to 30% of 2-phosphonobutane-1,2,4-tricarboxylic acid (PBTCA) and/or 5% to 20% of 2-hydroxyl-phosphino acetic acid (HPAA); and 10% to 30% of amino trimethylene phosphonic acid (ATMP) and/or 5% to 10% of 1-hydroxy ethylidene-1,1-diphosphonic acid (HEDP) and/or 10% to 20% of polyacrylic acid (PAA) and/or 5% to 20% of polymaleic anhydride (PMA); and 1% to 2% of benzotriazole (BTA) or 1% to 2% of methylbenzotriazole (TTA); and/or 10% to 20% of phosphono-carboxylic acid copolymer (MAHS) and rest amount of deionized water. The CaCO3 inhibiting performance and corrosion inhibiting performance of the present inhibitor surpass that of the IDA-II scale and corrosion inhibitor. The Zn<2+> stabilizing capacity of the present inhibitor also surpasses that of IDA-II inhibitor. When the present inhibitor is added with a dosage of 50mg/L to 100mg/L, the phosphorcontent in the cooling water is only 0.210mg/L (calculated according to PO4<3-> content), thus the phosphor content is below the limited phosphor discharging quantity (which is below or equal to 0.5m/L) within the primary standard.