NOVELTY - Method for preparing bio-diesel antioxidant additive through biomass microwave aided thermal decomposition comprises crashing plant cellulose material into grains, using inorganic acid dilute solution to dip the grains, draining, sending into microwave thermal decomposition device, collecting generated acetic acid, formic acid and methanol, collecting furfural and light biologic oil; absorbing the generated phenol relic, alkylating, and extracting alkylated phenol components with strong fat-solubility from ion liquid with organic solvent as bio-diesel antioxidant additive.    USE - Method for preparing bio-diesel antioxidant additive through biomass microwave aided thermal decomposition (claimed).    ADVANTAGE - The bio-diesel antioxidant additive has good oil solubility, strong antioxidant effect and low cost; the method uses target that plants cellulose biomass completely with green chemistry.    DETAILED DESCRIPTION - Method for preparing bio-diesel antioxidant additive through biomass microwave aided thermal decomposition comprises crashing plant cellulose material into grains with gain size 1-10 mm through interceptive crashing, using inorganic acid dilute solution to dip the grains for 1-24 hours, draining to dry, sending into microwave thermal decomposition device, ensuring air tightness of system, controlling temperature for thermal decomposition to be not greater than 120 degrees C, keeping for 10-30 minutes, collecting generated acetic acid, formic acid and methanol; controlling temperature for thermal decomposition to be not greater than 150 degrees C, keeping for 5-15 minutes, collecting furfural and light biologic oil; controlling temperature for thermal decomposition to be not greater than 500 degrees C to enable reductive incondensable gas components generated by crack circularly blow reaction area, keeping for 5-15 minutes to enable lignose of reaction material be maximally cracked into phenol relic with small molecular weight, absorbing the generated phenol relic by mixing medium of sulfonated ion liquid and alcohols, alkylating, and using organic solvent to extract out alkylated phenol components with strong fat-solubility from ion liquid as bio-diesel antioxidant additive.    DESCRIPTION OF DRAWING(S) - The drawing shows the schematic diagram of the biomass microwave aided thermal decomposition device.