The work aims to obtain the optimum conditions for inhibition efficiency, like proportion, concentration, etc. through the corrosion inhibition analysisof Q235 steel by TritonX-100(TX-100) and 2-mercaptobenzimidazole (MBI) mixed system in acid solution and analyze the corrosion inhibition efficiency and mechanism. The performance of corrosion inhibitor was preliminarily determined by weight loss method. The corrosion inhibition efficiency and mechanism were investigated furtherby polarization measurements and electrochemical impedance spectroscopy. The morphology and the chemical composition of metal surface in different conditions were observed by SEM and XPS. Corrosion inhibition mechanism of mixed corrosion inhibitor on carbon steel surface was studied by comprehensive analysis method. When the total concentration of the mixed corrosion inhibitor was kept at 2×10?4 mol/L and TX-100 and MBI were mixed by different molar ratios, the inhibition efficiency (η) increased with the increasing of α(TX-100). The value of η reached the largest 90% at α(TX-100)=50% and then decreased with the increasing of α(TX-100). When TX-100 and MBI were mixed with equal molar, η increased with the increasing of inhibitor concentration. The value of η did not increase distinctly with the increasing of inhibitor concentration that had reached 2×10?4 mol/L since η reached 90%. Molecular interaction existing between TX-100 and MBI led to the tight protective layer at the surface of Q235 steel. TX-100 and MBI were mixed inhibitors that controled the cathodic reaction mainly. Through optimized selection of the proportion and concentration of TX-100 and MBI, the dosage and cost of MBI are reduced and theoretical foundation is established for metal cor-rosion.