NOVELTY - Preparation of a biodiesel comprises heating a oil material, filtering and removing insoluble impurities, adding glycerin, carrying out pre-esterifying reaction under protection of inert gas at 150-350 degrees C and 350-600 mm Hg; mixing the glycerin mixture and methanol, adding sodium hydroxide or potassium hydroxide, carrying out transesterification reaction under protection of the inert gas at 50-80 degrees C; centrifugally separating; and centrifugally separating the methanol, and pre-esterifying reaction to the glycerin.    USE - Method for the preparation of biodiesel from oil material including waste oil in catering industry, hogwash oil, acidated oil, animal waste oils, or plants and non-refined crude oil of wood oil plant (claimed).    ADVANTAGE - The method adopts esterification-transesterification combining high-temperature glycerin esterification without using catalyst with high-efficient base catalyst transesterification.    DETAILED DESCRIPTION - Preparation of a biodiesel comprises:    (A) heating a oil material, filtering and removing insoluble impurities after fusing, adding glycerin, carrying out pre-esterifying reaction under protection of inert gas at 150-350 degrees C and 350-600 mm Hg, where the mole ratio of the glycerin to free fatty acid in the oil material is 0.3-1.5;    (B) mixing the glycerin mixture and methanol, adding sodium hydroxide or potassium hydroxide as catalyst, carrying out transesterification reaction under protection of the inert gas at 50-80 degrees C, where the mole ratio of methanol to glycerin ester is 4:1-9:1, and the dosage of the sodium hydroxide or potassium hydroxide is 0.8-0.2 wt.% of the glycerin ester;    (C) centrifugally separating the product, obtaining crude methyl ester light-phase and crude glycerin heavy-phase, obtaining biodiesel product and asphalt by decompressing and distilling under protection of an inert gas, washing, neutralizing the base catalyst in the crude glycerin, and carrying out decompressing and distilling to obtain methanol and glycerin; and    (D) centrifugally separating the methanol, and pre-esterifying reaction to the glycerin.    An INDEPENDENT CLAIM is included for a movable producing device.