Abstract: The effects of temperature, H₂S partial pressure and flow rate on the H₂S corrosion behavior of L80 steel were studied by using a high temperature and high pressure dynamic autoclave, and the corrosion products were analyzed by SEM and EDS. The high temperature resistant H₂S corrosion inhibitor LH-11 was selected to study its corrosion inhibition performance. The results showed that the H₂S corrosion rate of L80 steel reached the maximum at 80 ℃ and the minimum at 140 ℃; the corrosion rate of L80 steel increased with the increase of H₂S partial pressure, and gradually increased with the increase of flow rate. The corrosion products were mainly sulphur-iron compounds with loose and irregular structure and pores. The corrosion inhibition rate of the corrosion inhibitor LH-11 to the steel could reach 87.05%, and the temperature resistance was 180 ℃. After adding the corrosion inhibitor, the corrosion rate of the steel could be reduced to less than 0.1 mm/a. The corrosion inhibitor was suitable for different H₂S partial pressure and different flow rate conditions, and could play a good role in protecting the thermal recovery string.