Abstract: There are roughly three automatic metering methods for oil tank, that is static pressure type, liquid level type, and mixing type. Through analyzing the functions of the three methods, it is concluded that the static pressure method is suitable for static supervision and oil unloading supervision, which only meets the ordinary demands of automatic management of metering; liquid level method is suitable for the individual static supervision; while mixing method makes up for the defects of the former methods, which is not only able to meter oil and water level as well as to track and supervise the loading and unloading of oil, but also decreases the computation and increases the reliability of the metering system.