Abstract: In view of corrosion question of the bottom plates of oil storage tank, the authors carry on the microscopic observation and the examination using the electronic scanning electricity mirror (SEM) and the power spectrum analyzer to corrosion material surface of the bottom plates of oil storage tanks thoroughly study the bottom corrosion mechanism. The study indicates that the root of the corrosion of bottom plates is coming from the catalyzed unenlightened cell function of the chlorine ion; hydrogen sulfide along with the mutual effect of oxygen concentration cell beneath the oil residual matter result in the ulcer-like corrosion of bottom plate. The superiority of electronic scanning electricity mirror and the power spectrum analyzer is confirmed as effective in examination of oil storage tanks.