NOVELTY - Biodiesel is produced by heating the biodiesel, filtering, and drying by dehydration; adding the dried biodiesel to methanol containing 3% sulfuric acid; performing primary esterification reaction and secondary esterification reaction; vacuum drying the esterification reaction product; heating and distilling the secondary esterification reaction product; evaporating out the biodiesel and cooling so as to become liquid and obtain biodiesel product; and distilling the methanol solution, separating out the biodiesel, and recycling the methanol after cooling.    USE - Method of producing biodiesel (claimed).    ADVANTAGE - The method has stable technical process, simple operation, little investment, and transferring rate of 85%.    DETAILED DESCRIPTION - Production of biodiesel comprises:    (A) pre-treating biodiesel by heating to 65-70 degrees C and filtering to remove impurity;    (B) heating the biodiesel at 110 degrees C and vacuum degree of 0.085-0.09 MPa for 30 minutes with stirring at 30-60 rpm, and drying by dehydration;    (C) adding the dried biodiesel to methanol (10 plus minus 0.5 wt.%) containing 3% sulfuric acid, heating the mixture to 65-70 degrees C, stirring at 30-60 rpm, processing primary esterification for 1.5-2.5 hours so that the acid value of biodiesel after primary esterification reaction is reduced to 70%;    (D) adding methanol (40 plus minus 5 wt.%) and 3% sulfuric acid to the primary esterification product, uniformly stirring to process secondary esterification reaction for 9-12 hours at 65-70 degrees C, detecting acid value every 3 hours so that the acid value is reduced to 5-10;    (E) vacuum drying the second esterification reaction product, heating to 120 degrees C at vacuum degree of 0.085-0.09 MPa for 30 minutes with stirring at 30-60 rpm, and removing moisture content so that water is not greater than 3%;    (F) distilling the dried second esterification reaction product by heating to 220 degrees C at vacuum degree of 0.085-0.09 MPa, evaporating out the biodiesel, and cooling so as to become liquid and obtain the biodiesel product; and    (G) distilling methanol solution at 60-70 degrees C, separating out the biodiesel, and recycling the methanol after cooling with purity of 90%.