NOVELTY - Production of biodiesel comprises filtering impurities in waste oil, removing colloid impurities in oil through hydrate degumming and sulfate degumming, adding oil industrial methanol and acidic catalyst, esterifying, condensing vapor, and delaminating; adding upper acidic catalyst methanol solution, using alkaline catalyst and acidic catalyst in ester exchange reaction, and converting soap into grease; passing filtered mixed solution through methanol flashing tower, standing and delaminating; and introducing raw methyl ester to distilling kettle, and collecting fraction to obtain biodiesel.    USE - Method of preparation of biodiesel used for vehicles (claimed).    ADVANTAGE - The product produced is biodiesel capable of replacing 0# diesel; and the method utilizes easily obtained material, has simple production equipment, low cost, and high production efficiency and high product quality.    DETAILED DESCRIPTION - Production of biodiesel comprises:    (A) filtering impurities in waste oil, removing colloid impurities in oil through hydrate degumming and sulfate degumming, adding oil industrial methanol and acidic catalyst to esterification reactor connected to methanol rectifying tower at mass ratio of 1000:100-50:15-36, esterifying for 30-120 minutes at 70-120 degrees C, when methanol vapor and vapor generated in reaction passing through methanol rectifying tower, condensing vapor on bottom of methanol rectifying tower, returning methanol vapor to esterification reactor through fan to react, circulating methanol in gaseous phase form, standing reaction system, delaminating after esterification, with upper layer of catalyst methanol solution and lower layer of oil layer, and inducing upper layer and lower layer to different storage tank;    (B) sending material oil after esterifying and deacidifying to esterification reactor, with methanol of 15-45%, alkaline catalyst of 0.6-1.5%, and processing ester exchange reaction at 60-90 degrees C for 30-90 minutes;    (C) adding upper acidic catalyst methanol solution generated in esterification stage, using alkaline catalyst and acidic catalyst in ester exchange reaction to obtain acidic salt insoluble to organic system, converting soap into grease at 60-90 degrees C for 30-60 minutes, with acidic catalyst comprising sulfuric acid, and alkaline catalyst comprising potassium hydroxide or sodium hydroxide, with mass ratio of acidic catalyst to alkaline catalyst of 1:2.5;    (D) filtering reaction system to recover acidic salt generated by acid-alkali catalyst reaction as side product of biodiesel production, passing filtered mixed solution through methanol flashing tower to remover methanol, standing and delaminating, with lower layer of glycerol, and upper layer of raw methyl ester, and obtaining obtained raw methyl ester used as fuel oil;and    (E) introducing raw methyl ester to distilling kettle, with liquid phase temperature at 220-300 degrees C under 0.002-0.01 MPa, and collecting fraction to obtain biodiesel.    DESCRIPTION OF DRAWING(S) - The drawing shows a schematic diagram of the production of biodiesel. (Drawing includes non-English language text)