NOVELTY - Preparation of low pour point biodiesel through biological fermentation coupling comprises adding lipolytic bacteria-containing activated sludge into raw material grease; putting under shake cultivation; standing for layering, where upper layer is fatty acid; adding methanol and acidic catalyst into the fatty acid; carrying out esterification reaction; producing aqueous methanol steam and mixed product of esterification reaction; standing; separating the obtained mixed product; distilling and refining the crude biodiesel to remove methanol and residue; and obtaining biodiesel.    USE - Preparation of low pour point biodiesel (claimed).    ADVANTAGE - The method utilizes lipase produced by the metabolite of lipolytic bacteria to decompose the grease into short 10-16C-containing fatty acid; and the fatty acid is subjected to esterification reaction to obtain biodiesel having shorter carbon chains and much lower pour point compared with traditional biodiesel. It provides product with small viscosity and good low temperature fluidity; and has mild preparation condition and low energy consumption due to shortened carbon chain reaction under extremely low temperature.    DETAILED DESCRIPTION - Preparation of low pour point biodiesel through biological fermentation coupling comprises adding lipolytic bacteria-containing activated sludge (30-50 mass% of the mass of the raw material grease) into raw material grease; putting under shake cultivation for 10-20 days at 30-35 degrees C; standing for layering, where upper layer is fatty acid; adding methanol (20-50 mass% of the mass of fatty acid) and acidic catalyst (0.5-5 mass% of the mass of fatty acid) into the fatty acid; carrying out esterification reaction for 10-90 minutes at 0.1-0.12 MPa and 60-100 degrees C; producing aqueous methanol steam and mixed product of esterification reaction; standing; separating the obtained mixed product for 10-30 minutes at 0.08-0.1 MPa and 30-50 degrees C to obtain acidic catalyst at the lower layer and crude biodiesel at the upper layer; distilling and refining the crude biodiesel at 0.1-0.12 MPa and 140-250 degrees C to remove the methanol and residue; and obtaining biodiesel.