The high concentration of Cl − in seawater causes serious corrosion of copper and enormous economic losses. In order to reveal the microscopic mechanism and kinetic process of Cl − in different corrosion inhibition films, the diffusion of Cl − in benzotriazole, mercaptobenzothiazole and methyl benzene three nitrogen thiazole and the interaction between CuO (−1 0 0) and three corrosion inhibition films were researched by using molecular dynamic simulation. The research indicated that corrosion inhibition mechanisms of the three films are not the same. The inhibition of benzotriazole and methyl benzene three nitrogen thiazole is mainly because of direct chemical adsorption. However, the inhibition of mercaptobenzothiazole is because of indirect chemical adsorption. The diffusion coefficient of Cl − in benzotriazole, mercaptobenzothiazole and methyl benzene three nitrogen thiazole is 1·634 × 10 −5 , 1·656 × 10 −5 and 1·627 × 10 −5 cm 2 s −1 , respectively. All of them are relatively low, so the three inhibitors can effectively prevent Cl − diffusing into themselves. Furthermore, pore connectivity is worst for benzotriazole film and the membrane structure is more stable than that of methyl benzene three nitrogen thiazole and mercaptobenzothiazole.