NOVELTY - The method comprises introducing biodiesel crude product containing biodiesel, low-carbon alcohol (1-4C), ester compound (5-11C) and heavy oil (19-40C) into a first tower for distilling the alcohol at a pressure of 20-25 KPa, washing the crude product at 80-90 degrees C for 1-2 hours by water, introducing the crude product into a second tower for lightening and distilling the crude product at a pressure of 15-20 KPa, where the lightening and distilling condition enables a mixture containing water, a few amount of remained alcohol and the compound in a water-washed biodiesel crude product.    USE - The method is useful for refining a biodiesel crude product.    ADVANTAGE - The method is capable of economically refining the biodiesel crude product with high purity and quality in an environmentally manner.    DETAILED DESCRIPTION - The method comprises introducing biodiesel crude product containing biodiesel, low-carbon alcohol (1-4C), ester compound (5-11C) and heavy oil (19-40C) into a first tower for distilling the alcohol at a pressure of 20-25 KPa, washing the biodiesel crude product at 80-90 degrees C for 1-2 hours by water, introducing the biodiesel crude product into a second tower for lightening and distilling the crude product at a pressure of 15-20 KPa, where the lightening and distilling condition enables a mixture containing water, a few amount of remained low-carbon alcohol and the compound in a water-washed biodiesel crude product to be recovered from a tower top and enables a mixture of the biodiesel and the heavy oil to be recovered from a tower bottom, and introducing the mixture of the biodiesel and the heavy oil into a flash evaporation tower for treating the mixture at a pressure of 0.65-1.5 KPa and a temperature of 240-280 degrees C by flash evaporation condition, where the flash evaporation condition enables: the biodiesel to be recovered from a tower top of the flash evaporation tower; and the heavy oil to be recovered from a tower bottom of the flash evaporation tower, where a part of the compound recovered from a tower top of the second distilling tower is returned into the second distilling tower. The lightening and distilling condition enables the amount of the compound in the mixture of the biodiesel and the ester compound recovered from the tower bottom to be less than or equal to 2 wt.%. The flash evaporation condition enables a content of the heavy oil in the biodiesel recovered from the tower top to be less than or equal to 0.4 wt%. A temperature of the tower top of the alcohol distillation is 60-70 degrees C. A temperature of the tower bottom of the alcohol distillation is 80-90 degrees C. A ratio of the amount of the washing water to the weight of the crude product is 0.1-0.3: 1. The crude product is obtained by transesterification method.