The corrosion inhibition performances of thiourea (TU), l-cysteine (CYS), sodium dodecyl sulfonate (SDS), tetradecyl trimethyl ammonium bromide (TTAB), N-benzyl pyridinium chloride (BPC) and imidazoline quaternary ammonium salt (IAS) in CO₂-saturated and CO₂/H₂S coexistent brine solutions were investigated by electrochemical measurement, weight-loss test, molecular dynamics simulation and SEM observation. The results show that H₂S can remarkably affect the adsorption of some inhibitors on the steel surface and the inhibition performance. In detail, the inhibition performances of TU, CYS and SDS, which are effective in the CO₂ environment, deteriorate in the CO₂/H₂S environment. However, the cationic inhibitors (TTAB, BPC and IAS) exhibit good inhibition performance in the CO₂/H₂S environment possibly because of a relatively strong interaction between inhibitor cations and HS⁻ ions. The finding of this study delivers a provable method to predict the performance of inhibitors in the aggressive solution containing H₂S.