The invention discloses a method for modifying biomass cracking oil to modified biomass oil through esterification, etherification and quality-improvement. The method comprises the following: step one, according to the proportion that the mass ratio of biomass cracking oil to benzyl chloride to alkaline solution to low-carbon alcohol is 100 to 80-100 to 40-80 to 10-20; and the biomass cracking oil, the low-carbon alcohol, the benzyl chloride and the alkaline solution are added into a reaction kettle, are heated at the temperature of between 90 and 110 DEG C to an infinite reflux state and react for 5 to 8 hours. Step two, after the infinite reflux reaction is finished, the mixture is cooled, condensed and layered; the lower layer is clear and transparent aqueous solution; black oil phase on the upper layer is separated, and is distilled under the condition that the temperature is 80 DEG C and the pressure is 10 kilopascal; low-carbon alcohol and water in oil phase are removed; the residual mixture is distilled under the condition that the temperature is between 130 and 150 DEG C and the pressure is 10 kilopascal; the unreacted benzyl chloride is reclaimed to obtain a product of black viscous liquid; and according to the proportion that the mass ratio of the product to ethanol is 3 to 1, the black viscous liquid is diluted and dissolved to obtain the modified biomass oil of which the PH value is between 5 and 7, the density is between 1.0 and 1.1 g/cm<3>, the water content is between 0.5 and 1.0 percent, the thermal value is between 25.0 and 35.0 kJ/g and the viscidity is between 135 and 150 mm<2>/s.