Aiming at the oil and gas well environment with high content of CO2，H2S and Cl-，1-（2-naphthyl- thioureaethyl）- 2-pentadecyl-imidazoline corrosion inhibitor was prepared from hexadecanoic acid，diethylenetriamine and 1-naphthyl-2-thiourea. In the salt solution with saturated concentration of CO2，H2S mass concentration of 30 mg/L and Cl- mass fraction of 0—30%，the effect of corrosion inhibitor on the corrosion morphology and corrosion inhibition effect of the steel sheet was studied. The corrosion inhibition mechanism was analyzed through electrochemical polarization curves and AC impedance spectroscopy. The results showed that Cl- accelerated the corrosion of carbon steel in CO2/H2S medium. In the salt solution containing saturated CO2，30 mg/L H2S and 10% Cl-，the corrosion inhibitor could slow down the corrosion of carbon steel by Cl- . The inhibition effect of corrosion inhibitor decreased with increasing Cl- concentration. When the Cl- content was less than 20%，the inhibition effect was better. As the concentration of corrosion inhibitor increased，the corrosion inhibition rate increased and gradually stabilized. When the amount of corrosion inhibitor was 100 mg/L，the corrosion inhibition rate was 94.36% . The corrosion inhibitor was a mixed corrosion inhibitor that could inhibit the action of cathode and anode. It could form a dense protective film on the surface of carbon steel， hinder the contact between corrosion medium and metal matrix，and inhibit the corrosion of metal. The corrosion inhibitor could be used for the corrosion inhibition of pipelines with high content of CO2，H2S and Cl-.