Inhibition of the 1045 carbon steel corrosion by methionine and proline in PCMs solution have been investigated. Electrochemical measurements show that these inhibitors can protect steel against corrosion, with a maximal protection efficiency up to 95.0% by methionine/proline compound inhibitor at molar ratio equal to 5:3. All inhibitors act as anodic-type inhibitor. FESEM, EDS, XRD characterization indicates that the corrosion of steel starts from pitting corrosion of Cl− ion, and gradually evolves into a general corrosion. The NH4FePO4·nH2O, Fe2O3 are the main corrosion products. XPS study confirms that Met and Pro molecule can adsorb on steel surface and form inhibition films. The inhibition mechanism was further investigated through theoretical modeling studies.