The work aims to reduce corrosion resistance of Cl ions in wastewater by adding corrosion inhibitor in industrial wastewater, so as to make the wastewater cooling water in production and realize energy conservation and environmental protection. The effects of wastewater temperature on corrosion rate of Q235 steel were studied in weight loss method to determine corrosion temperature of wastewater. Optimal volume of L-ascorbic acid and L-cysteine in wastewater was studied, a compound corrosion inhibitor was prepared, and optimal time for the formation of compound corrosion inhibitor film was investigated. Self-corrosion current density, polarization corrosion current density and polarization impedance of Q235 steel with and without complex corrosion inhibitor film was studied in the methods of Tafel curve, anodic polarization curve and AC impedance, respectively. Morphological changes of the film before and after corrosion were studied with SEM. The optimal volume of L-ascorbic acid was 165 mg/L and L-cysteine 18 mg/L in the industrial wastewater at 60 ℃. Formation time of the compound corrosion inhibitor film was 24 h. The self-corrosion current density of Q235 steel without corrosion inhibitor film was 4.918?10?5 A/cm2. The polarization corrosion current density was 1.667?10?2 A/cm2 and polarization impedance was 529 Ω?cm2 at overpotential of 500 mV. The self-corrosion current density of Q235 sheet steel with complex corrosion inhibitor film was 3.433?10?7 A/cm2, polarization corrosion current density was 4.132?10?6 A/cm2, and the polarization impedance was high. Inhibition rate of the compound corrosion inhibitor was 80.15%, significantly higher than that of a single inhibitor. SEM test showed that Q235 steel without corrosion inhibitor film was severely corroded and that with corrosion inhibitor film was barely corroded at overpotential of 500 mV. Corrosion resistance of the industrial wastewater of PVC heat stabilizer is improved by adding moderate amount of corrosion inhibitor, the wastewater basically meets the requirement for cooling water.