The corrosion inhibition of PBA on the Q235 steel in 1 M hydrochloric acid solution and its adsorption behavior on the Q235 steel surface were studied by means of weight loss method, electrochemical tech-nique and atomic force microscope (AFM) observation. Results show that PBA is a mixed inhibitor that inhibits both cathode and anode. the inhibition efficiency increases with the increase of PBA concentra-tion, and decreases slightly with the increase of temperature, when the mass concentration of PBA is 80 mg/L, the inhibition efficiency is the best. The adsorption of PBA on the carbon steel surface is exothermic, following the Langmuir's adsorption isotherm, which is a mixed adsorption based on chemical adsorption. PBA formed a compact protective film on the steel surface, which greatly hindered the steel corrosion. The inhibition mechanism of PBA was analyzed by quantum chemical method, these results indicate that the active sites of PBA are concentrated on the benzene ring and the heterocyclic ring, and the ability of PBA molecules to accept electrons is greater than the ability to provide electrons.