The corrosion inhibition performances of three single-component corrosion inhibitors of polyepoxysuccinic acid (PESA), polyaspartic acid (PASP) and sodium gluconate (Glu) for carbon steel were tested by the static weightlessness method. Then the three agents were combined with each other in an orthogonal way to form a composite inhibitor of PESA/PASP/Glu with a high corrosion inhibition performance on carbon steel. Finally, the effects of the addition concentration, test the time, temperature and pH on the corrosion inhibition of the composite agents were investigated. The composite agents showed a corossion inhibition rate of 94.6% under the optimal concentration of 1000 mg?L-1. The corrosion inhibition rate decreased gradually with time but remained above 70% at 48 h. With temperature increased, the corrosion inhibition rate reduced slightly and still reached 86.5% at 80℃. Higher corrosion inhibition rate was found at higher solution pH. The corrosion inhibition rate is 96.5% at pH 12, almost completely inhibiting the corrosion of carbon steel. These results indicated that the phosphorus-free composite corrosion inhibitor was especially suitable for high temperature and high alkalinity system.