Abstract: Electrochemical test was used to research the optimum compound proportion of imidazoline quaternary ammonium salt (IM) and octylphenol ethoxylate (OP). X-ray photoelectron spectroscopy (XPS) was used to analyze the adsorption characteristics of the corrosion inhibitor on the surface of L245 steel under the corrosion conditions of high temperature and high pressure with CO₂. The inhibition mechanism of the compound inhibitors were studied by molecular dynamics simulation. The results show that the IM molecules adsorbing on the metal surface increased after being compounded. The adsorption of OP molecules enhanced the adsorption of IM molecules on the metal surface, and a compact protective film was formed to hinder the corrosive media in solution from corroding metal surface and protect the substrate from corrosion effectively. So the inhibition efficiency of IM compounded with OP obviously increased. The adsorption intensity of inhibitor molecules on Fe (001) surface increased after the addition of IM compounded with OP, which indicates that the corrosion inhibition of inhibitor molecules is determined by the electron transfer behavior of inhibitor molecules on the metal surface.