Abstract: Sunflower head extract (Helianthus annuus L. extract, HALE) obtained by ultrasonic assisted extraction was used as an inhibitor. The corrosion inhibition of HALE to carbon steel in 0.5 mol/L H₂SO₄ solution was studied in corrosion immersion test and electrochemical testing. The results show that HALE had a good corrosion inhibition effect to carbon steel, and the corrosion inhibition rate increased with the increase of HALE dosage, but decreased with the increase of temperature. The adsorption of HALE on the surface of carbon steel conformed to the Langmuir adsorption model and was a mixed adsorption based on physical adsorption. Electrochemical test results showed that HALE was an anode-based mixed inhibitor corrosion inhibitor.