NOVELTY - Biomass based diesel oil comprises (wt.%) mixed fatty acid methyl ester, fatty acid ethyl ester, and fatty acid butyl ester (3-10); butanol and isobutanol (2-5); copolymer of carbonate rare earth lanthanum cerium polylol oleate (0.1-0.3); and 12-14C alkane and 12-14C isoparaffin (balance).    USE - Biomass based diesel oil used as environment-friendly solvent, and for replacing diesel oil fuel.    ADVANTAGE - The diesel oil has high thermal value, high cleanness degree, low coagulation point and good stability.    DETAILED DESCRIPTION - An INDEPENDENT CLAIM is included for a preparation of biomass based diesel oil comprising:    (A) pressurizing and filtering bio-oil prepared by pyrolysizing and plant oil with Cx fatty acid of 35-40%, under 0.8-1 MPa, dehydrating, removing solid impurities (colloid, resin, unsaponifiable matter and inorganic matter), and sending to buffer tank and to high pressure oil pump;    (B) introducing hydrogen to separating tank, removing moisture content in air under pressure 1-1.2 MPa, making content of moisture not more than 0.5 mu g/g, and sending to three-stage reciprocating compressor;    (C) using high pressure hydrocracking, with fixed bed reactor and in single segment of series full cycle hydrocracking, using refining catalyst as non-noble metal nickel series component, molecular sieve, rare earth lanthanum, cerium; in the hydrogen refining reactor, controlling reaction temperature at 300-320 degrees C, under 10-130 MPa, for 3-5 minutes; in hydrocracking reactor, controlling reaction temperature at 320-400 degrees C, under 12-15 MPa, controlling iodine at lower than 85 for 13-15 minutes; operation parameters of refining reactor are: condition: hydrogen partial pressure (MPa): 10-13; condition: reaction temperature ( degrees C): 300-320; condition: air speed (/hour): 0.8-1.8; condition: volume ratio of hydrogen to oil; parameter: 800-1000; operation parameters of hydrocracking reactor are; condition (MPa): 12-15; condition: reaction temperature ( degrees C): 320-400; condition: air speed (/hour): 0.8-1.8; condition: volume ratio of hydrogen to oil; parameter: 1200-1700;    (D) using back hydrogen mixing, hot high pressure separating technology flow, standing and extracting to separate excessive hydrogen, water and other components; cooling reaction product from reactor by exchanging heat, cooling at 160-180 degrees C then entering high pressure separator, separating hydrogen (H2), water (H2O) and oil component in reaction product, producing separated gas having 90-95 vol.% H2, after pressurizing by recycle compressor, using most part as recycle hydrogen, and using small part for pre-treating;    (E) using recycle depressurizing and fractionating tower to volatilize Cx light hydrocarbon in the oil, directly recovering light hydrocarbon and sending to fuel gas pipeline;and    (F) screening components obtained by fractionating tower having 12-14C alkane and 12-14C isoparaffin, adding rare earth high molecular material functional additive copolymer of carbonate rare earth lanthanum cerium polylol oleate (0.1-0.3 at.%), fatty acid methyl ester, fatty acid ethyl ester and fatty acid butyl ester (3-10 at.%), butanol and isobutanol (2-5%), and filtering after uniformly mixing to obtain high performance biomass based diesel oil.    For Cx fatty acid,x= not greater than 18.    For Cx light hydrocarbon,    x= not greater than 4.    DESCRIPTION OF DRAWING(S) - The drawing shows a schematic diagram of the preparation of biomass based diesel oil. (Drawing includes non-English language text).