Five corrosion inhibitors have been evaluated in high temperature naphthenic acid environment: triethyl phosphate(A), dioctylphosphoric acid(B), triphenyl phosphate(C), tetraethylenepentamine(D) and 1 aminoethyl 2 dodecylimidazoline(E). It is found that A, B and C have good inhibitory property and the corrosion inhibitory efficiency increases linearly with the hydrophilicity of inhibitor molecule; polyamine compound, being a corrosion inhibitor, reacts also with naphthenic acid to produce azole or amide compounds, which also behave as inhibitors. Five corrosion inhibitors have been evaluated in high temperature naphthenic acid environment: triethyl phosphate (A), dioctylphosphoric acid (B), triphenyl phosphate (C), tetraethylenepentamine (D) and 1 aminoethyl 2 dodecylimidazoline (E) B and C have good inhibitory property and the corrosion inhibitory efficiency increases linearly with the hydrophilicity of inhibitor molecule; polyamine compound, being a corrosion inhibitor, reacts also with naphthenic acid to produce azole or amide compounds, which also behave as inhibitors.