The work aims to develop green natural corrosion inhibitor in the field of hydrochloric acid cleaning, and study corrosion inhibition effect of Galium Aparine Linn extracts (GALE) on Q235 steel in 1 mol/L HCl. Plant corrosion inhibitor was extracted from Galium Aparine Linn stems and leaves in the method of 95% ethanol extraction. Main functional groups of GALE were characterized with Fourier Transform Infrared (FTIR) spectroscopy. Corrosion inhibition effect of GALE on Q235 steel in 1 mol/L HCl was investigated in the methods of weight loss, polarization curves and electrochemical impedance spectroscopy (EIS), and corrosion inhibition mechanism of GALE was also discussed. The GALE could effectively inhibit corrosion of Q235 steel in 1 mol/L HCl medium, it acted as a mixed-type inhibitor mainly featuring in cathodic control. Inhibition efficiency increased as the GALE concentration increased and was up to over 82% at 25 ℃ when GALE mass concentration was 1.2 g/L, which was slightly affected by soaking time. Its inhibition mechanism was “geometric covering effect”. Adsorption of effective corrosion ingredients on Q235 steel conformed to Langrnuir isotherm and belonged to physical adsorption, and equilibrium constant was 10.62 L/g. The GALE is an effective inhibitor for Q235 steel in 1 mol/L HCl solution medium, and is also a kind of environment-friendly corrosion inhibitor of certain application value in the field of hydrochloric acid cleaning.