NOVELTY - Biodiesel is prepared by adding plant oil and low carbon alcohol with mole ratio of 1:(2-3), 1-2% heterogeneous alkali catalyst, and less than or equal to 8% alkane co-solvent with respect to total weight of reaction system into reactor to perform base-catalyzed transesterification reaction, fully reacting intermediate reaction product, adding intermediate reaction product into decompressing and distilling device to distill at 65-70 degrees C to remove co-solvent by reacted intermediate reaction product, precipitating and separating to remove heterogeneous alkali catalyst, and adding 1-2% lipase.    USE - Preparation of biodiesel (claimed).    ADVANTAGE - Preparation of biodiesel has lower reaction temperature, higher lipase transferring rate, lower requirements for production device, and lower production energy consumption.    DETAILED DESCRIPTION - Biodiesel is prepared by adding plant oil and low carbon alcohol with mole ratio of 1:(2-3), 1-2% heterogeneous alkali catalyst, and less than or equal to 8% alkane co-solvent with respect to total weight of reaction system into reactor to perform base-catalyzed transesterification reaction, fully reacting intermediate reaction product, adding intermediate reaction product into decompressing and distilling device to distill at 65-70 degrees C to remove co-solvent by reacted intermediate reaction product, precipitating and separating to remove heterogeneous alkali catalyst, and adding 1-2% lipase with respect to weight of reaction system to purified intermediate reaction product clear solution to perform lipase-catalyzed transesterification, wherein biodiesel product has greater than or equal to 99% transesterification reaction rate.    DESCRIPTION OF DRAWING(S) - The drawing shows a gas chromatography-mass spectrometry (GCMS) chromatogram of the intermediate reaction product supernatant after 3 hours of lipase transesterification reaction by adding methyl palmitate (a), stearic acid methyl ester (b), methyl oleate (c), and linoleic acid (d).