Abstract: The paper summarizes and analyzes the corrosion of oil tanks located in cave. The results show that the major corrosion cause is the water existed in the bottom plate of tank, whhich makes the conductive coating of bottom plate failed and fallen. The coating corrosion mechanism for the overall/partial fallen coatings of bottom plates is analyzed. It suggestes that the impressed current CP be used to protect the bottom plates, the dehydrator be reformed, and the corrosion inhibitor be added to the water.