NOVELTY - A biodiesel is esterified by mixing methanol and oil at a mass ratio of 1.5-2:1, heating at 70-80 degrees C, and atomizing the mixture to obtain atomized particles; and mixing concentrated sulfuric acid (1-1.5 wt.%) having a concentration of 98 mass% and methanol, adding obtained solution to the atomized particles, stirring to 60-100 minutes, esterifying at 70-80 degrees C, converting free fatty acid in the oil to methyl fatty acid to reduce acid value of oil to lower than 2 mg potassium hydroxide/g, recovering the methanol and sulfuric acid, and holding oil in an esterification chamber.    USE - Method of esterifying a biodiesel.    ADVANTAGE - The method is simple, and has low energy consumption, low production cost and good de-acidifying performance.    DETAILED DESCRIPTION - A biodiesel is esterified by:    (A) mixing methanol and oil at a mass ratio of 1.5-2:1, heating at 70-80 degrees C, and atomizing the mixture to obtain atomized particles;    (B) mixing concentrated sulfuric acid (1-1.5 wt.%) having a concentration of 98 mass% and methanol, adding obtained solution to the atomized particles, stirring to 60-100 minutes, esterifying at 70-80 degrees C, converting free fatty acid in the oil to methyl fatty acid to reduce acid value of oil to lower than 2 mg potassium hydroxide/g, recovering the methanol and sulfuric acid, and holding oil in an esterification chamber;    (C) mixing recovered product and methanol (1.8 times), adding potassium hydroxide (1 wt.%), heating at 75-85 degrees C, and atomizing to obtain atomized particles A;    (D) atomizing the oil in the esterification chamber, adding atomized particles A, esterifying at 75-85 degrees C for 60-150 minutes while stirring to obtain mixed solution comprising methyl fatty acid, glycerol, methanol, potassium hydroxide and water; and    (E) heating the mixed solution for 30-60min to form an upper layer comprising methyl fatty acid and a low layer comprising methanol-potassium hydroxide-glycerol-water mixed solution, refining the upper layer to obtain biodiesel, and discharging the lower layer.    An INDEPENDENT CLAIM is included for a device comprising an atomizer fan, a reaction chamber turbine stirrer, an ultrasonic generator, a esterification chamber, an upper liquid circulation loop shunt, a lower liquid circulation loop shunt, a methanol- acid catalyst storage chamber, a methanol- basic catalyst storage chamber, an oil storage chamber, a methanol-catalyst atomizing chamber, an oil atomizing chamber, a pre-mixer, a pre-mixer dewatering device, and a floating aspirator.    DESCRIPTION OF DRAWING(S) - The drawing is a flow chart of a method of esterifying a biodiesel (Drawing includes non-English language text).