NOVELTY - Fast pyrolysis preparation of bio-oil comprises crushing then drying biomass; carrying out fast pyrolysis reaction to generate pyrolysis gas and charcoal; separating pyrolysis gas; rough filtering pyrolysis gas to remove solid impurities; condensing into bio-oil; fine filtering pyrolysis non-condensable gas; removing water vapor, carbon monoxide, carbon dioxide, and acidic organic gas; condensing fourth stage pyrolysis gas to obtain bio-oil; and mixing separated vapor, acidic gas, carbon monoxide and carbon dioxide, condensing obtain acidic condensed liquid.    USE - Method for fast pyrolysis preparing bio-oil (claimed).    ADVANTAGE - The bio-oil has low water content and low acidity.    DETAILED DESCRIPTION - Fast pyrolysis preparation of bio-oil comprises:    (A) crushing biomass material to granularity of 0.6-1.2 mm, drying until water content of 6-12%;    (B) carrying out fast pyrolysis reaction at 400-550 degrees C for 0.5-3 seconds to generate pyrolysis gas and charcoal;    (C) separating pyrolysis gas and carbon;    (D) roughly filtering pyrolysis gas to remove solid impurities;    (E) carrying out first condensation of pyrolysis gas at 140-150 degrees C, where first stage pyrolysis condensable gas is condensed into bio-oil;    (F) fine filtering first level pyrolysis gas non-condensable gas to remove solid impurity and obtain secondary pyrolysis gas;    (G) removing water vapor, carbon monoxide and carbon dioxide to obtain secondary pyrolysis gas;    (H) separating pyrolysis gas to obtain third stage pyrolysis gas, and removing acidic organic gas to obtain fourth-stage pyrolysis gas;    (I) condensing fourth stage pyrolysis gas at 10-25 degrees C to obtain bio-oil; and    (J) mixing separated vapor, acidic gas, carbon monoxide and carbon dioxide, separating mixed gas, condensing at 10-25 degrees C to obtain acidic condensed liquid.    An INDEPENDENT CLAIM is included for fast pyrolysis bio-oil preparation device comprising pyrolysis reactor (1), cyclone separator (2), rough filter (3), first level condenser (4), and precise filter (5).    DESCRIPTION OF DRAWING(S) - The drawing shows a structure schematic diagram of fast pyrolysis bio-oil preparation device (Drawing includes non-English language text).    Pyrolysis reactor (1)    Cyclone separator (2)    Rough filter (3)    First level condenser (4)    Precise filter (5)