The ability of IMC-80BH corrosion inhibitor is proven to be excellent in earlier indoor static and flowing evaluation and it is worthwhile to determine the inhibitor concentration to maintain the optimum concentration for the sake of effective gas well protection. A improved concentration determination method is aboratively investigated. The maximum absorption wavelengths, buffer solution, reaction time and additive dosage of chromogenic reagent XD are detected successively and the standard curve of liquid phase behaves better than oil gas. The sample verification demonstrates that such determination measurement is reliable and precise. The four representative gas wells including G8-7, S59, W26-5 and G49-6 in service are also determined. The determination result offered substantial basis to analyze and select appropriate inhibitor injection program and dosage.