A quaternary corrosion inhibitor formula without phosphorus, which has a good synergistic effect was conformed in natural seawater through measuring corrosion rate and corrosion rate with the weight loss method. Corrosion mechanism of the compound corrosion inhibitors was studied through the electrochemical polarization, SEM and EDS analysis method. The results indicate that the inhibition efficiency is over 90 % in the proportion of 40 mg / L stungstate,40 mg / L sodium gluconate,4 mg / L Zn²⁺and 30 mg / L TEA. The compound inhibitor is an anodic corrosion inhibitor which formes a compact film on carbon steel surface, the main composition of the film is iron oxide with some W and Zn.