NOVELTY - Preparing biodiesel involves adding lipid, fatty alcohol and potassium fluoride-montmorillonite solid base catalyst in a reaction vessel and then performing transesterification reaction, where mass percentage of fluoride-montmorillonite solid base catalyst is 1-4 wt.% and the mole ratio of fatty alcohol and lipid is 8-15:1. The obtained material is heated on water bath at 50-80 degrees C and at pressure 2- 6 megapascal, where the liquid volume space velocity 0.3-4 per hour. The heated material is added into a distilling jar for distilling fatty alcohol and for separating glycerol.    USE - Method for preparing biodiesel (claimed).    ADVANTAGE - The method enables to prepare biodiesel in simple and cost-effective manner, and with high purity and yield.    DETAILED DESCRIPTION - Preparing biodiesel involves adding lipid, fatty alcohol and potassium fluoride-montmorillonite solid base catalyst in a reaction vessel and then performing transesterification reaction, where mass percentage of fluoride-montmorillonite solid base catalyst is 1-4 wt.% and the mole ratio of fatty alcohol and lipid is 8-15:1. The obtained material is heated on water bath at 50-80 degrees C and at pressure 2- 6 megapascal, where the liquid volume space velocity 0.3-4 per hour. The heated material is added into a distilling jar for distilling fatty alcohol and for separating glycerol. The separated material is added with non-ionic surface active agent as filter aid and then fatty acid monoglyceride is separated through the ceramic membrane separation to obtain high purity biological diesel oil. The hydrophilic lipophilic balance value of the non-ionic surface active agent is 3-25, non-ionic surface active agent dosage is 0.1-10 wt.%, the ceramic film support material is ceramic, film layer material is inorganic membrane, inorganic membrane is selected from aluminum oxide or titanium oxide, ceramic film aperture is 0.02-1.4 microns, and the film separating operation is performed at a temperature of 10-120 degrees C.