NOVELTY - Biodiesel with low condensation point is prepared from oil with high acid value by preatreating high acid value oil with aluminum sulfate; performing esterification reaction by reacting mixture of methanol and ethanol and pretreated oil in presence of catalyst including tungsten molybdophosphate to obtain esterified product; performing ester exchange reaction by reacting alcohol including ethanol and/or isopropanol and esterified product to obtain raw biodiesel; and recovering alcohol from raw biodiesel, standing to obtain upper layer as biodiesel product, and refining biodiesel oil layer.    USE - Method for preparing biodiesel with low condensation point from oil with high acid value (claimed).    ADVANTAGE - The method is easy to carry out and improves low temperature fluidity of biodiesel. It utilizes tungsten molybdophosphate solid catalyst in esterification reaction to replace concentrated sulfuric acid, and uses ethanol and isopropanol in ester exchange reaction to accelerate conversion of glyceride.    DETAILED DESCRIPTION - Preparation of biodiesel with low condensation point from oil with high acid value, comprises:    (A) mixing high acid value oil with 5-10% aluminum sulfate at volume ratio of 1:0.5-1 for 10-30 minutes at 60-80 degrees C, and standing for 1-3 hours, delaminating and separating out water phase, dewatering the oil phase at 110-115 degrees C till concentration of water is lower than 0.5 mass% to obtain pretreated oil;    (B) performing esterification reaction by stirring and reacting alcohol (mixture of methanol and ethanol) and the pretreated oil at mass ratio of 1-3:1 for 30-60 minutes at 60-85 degrees C in presence of 0.5-1.5 mass% catalyst (selected from tungsten molybdophosphate, tungsten phosphate, tungsten oxide, and/or zirconium oxide) to obtain esterified product;    (C) performing ester exchange reaction by stirring and reacting alcohol (selected from methanol, ethanol, and/or isopropanol) and the esterified product at mass ratio of 3-8:1 for 60-90 minutes at 65-75 degrees C in presence of 0.5-1.5 mass% catalyst selected from potassium hydroxide, potassium oxide-aluminum oxide, and/or magnesium oxide-aluminum oxide catalyst, to obtain raw biodiesel;    (D) recovering alcohol from the raw biodiesel, standing the oil and delaminating to obtain upper layer as biodiesel product and lower layer as glycerol and catalyst layer which is discharged; and    (E) refining the biodiesel oil layer to obtain the needed biodiesel with low condensation point.