Abstract: The shell of steel dome-roof oil tank is often eroded by rain, which affects the surface cleanliness of tank shell and corrodes it to result in shortening service life of coating and insulator and overhaul period, and furthermore corroding the bottom plate of the tank. Therefore, it is necessary to mend the design standards of tank, or rehabilitate the drainage system of tank during overhaul. Experiences show that setting up the flowing passageway, water retaining device and special drainage tube for oil tank can effectively control the rain water's erosion and corrosion.