Abstract: Find out the corrosion weakness of the atmospheric and vacuum distillation unit, it is convenient for daily maintenance and regular maintenance. The corrosion investigation of three sets of atmospheric and vacuum distillation equipment was carried out, and the results were collected and analyzed. The results show that the corrosion of the atmospheric and vacuum distillation unit was mainly concentrated in the atmospheric pressure system and the decompression system. The corrosion type of the atmospheric pressure system was mainly H₂S+HCl+NH₃+CO₂+H₂O corrosion of the atmospheric pressure tower system. The corrosion type of the decompression system was mainly the high temperature sulfur/naphthenic acid corrosion in the middle of the decompression tower. The monitoring of sulfur and chloride ion content in crude oil should be strengthened, and appropriate production process should be selected to improve the corrosion condition.