The corrosion behavior of 2205 duplex stainless steel (DSS) in hydrofluoric acid (HF) was affected by the chlorine ion. The methods including immersion, potentiodynamic polarization and electrochemical impedance spectra (EIS) were used to understand the effect. The results showed that while the NaCl concentration was added into HF solution from 0.015 mol/L to 0.030 mol/L, the corrosion potential got more positive, and the corrosion current density and average corrosion rate increased with the increasing NaCl content. It was because that NaCl decreased the pH of HF solution.