The influence of amino acids on the corrosion behaviour of steel in H2SO4solutions was studied by potentiodynamic polarization, AC impedance and weight-loss. The Potentiodynamic polarization curve results show that compound amino acids are mixed-type inhibitors which inhibit the reactions of anode and cathode; AC impedance results show that the ternary complex inhibitors have a good synergistic effect and high corrosion rate which can be proved by Resistance (Rt), double-layer capacitance (Cdl), Resistance modulus(︱Z︱), and phase angle from the Nyquist chart, Bode chart and phase angle chart. The weight-loss method show that the corrosion efficiency of composite amino acids are over 90% in 0-16 hours, 30-50°Cand 0.4-2.0mol / L sulfuric acid.