The corrosion inhibition performance and inhibition mechanism of L-phenylalanine(LPHA) for Q235 steel in 0.5mol/L H2SO4 solutions were evaluated using electrochemical methods. The corrosion inhibitor type was analyzed. The results indicated that the inhibition efficiency of LPHA for Q235 steel in 0.5 mol/L H2SO4 solutions increased with increasing the concentration of LPHA,and with increasing temperature, due to the increase of the number of inhibitor molecules adsorbed on one active site,the inhibition efficiency increased; LPHA was a mixed-type inhibitor and the inhibition mechanism of which was coverage effect. The adsorption of LPHA on the surface of Q235 steel was monolayer adsorption and conformed with El-Awa dydynamic model.