The crude oil is output by the oil feed pump from the oil tank, and next enters the crude oil heat exchanger to recover part of heat after metering and then is heated to the required temperature by the heater. After that, the oil is mixed with the metered phosphoric acid or citric acid from phosphate tank in the gas mixture (M401), and then enters the conditioning tank (R401) to make the nonhydratable phospholipids in oil change into the hydratable phospholipids. Add the alkali for neutralization, and the alkali quantity and alkali solution concentration depend on the quality of the crude oil. Through the heater, the neutralized oil is heated to the temperature (90℃) suitable for centrifugal separation to remove the phospholipids, FFA and other impurities in the crude oil. Then the oil goes to the washing process.