Abstract: It is not scientific and rational to calibrate the oil volume of vertical metal tank in line with the usual procedure like as tank cleaning and remeasuring after tank overhaul-Therefore, a new measurement method is suggested in this paper for oil volume calibration of vertical metal tank without tank-cleaning under running condition.Furthermore, the main devices and operation parameters needed in the measurement are pointed out clearly, Based on the oil level control, steps to measure the diameters (or circumference) for each tank ring, tank reference height, floating cover diameter, total mass, tank bottom and overlap parameters and other accessory parts in tank are systematically discussed-The uncertainty of this method proposed is less than 0.1%, which meets the needs of the volume calibration standard for metal oil tank, At present, this method has been widely applied in Huangdao Oil Tankfarm.