A method for modifying bio-oil derived from biomass pyrolysis, the method including: 1) adding an inorganic salt and an organic demulsifier to a bio-oil; oscillating or stirring the resulting mixture, and resting the resulting mixture, to yield a lower layer being an aqueous solution and an upper layer being the bio-oil, and collecting the bio-oil; 2) employing a zeolite molecular sieve-loaded clay as a catalyst, and aging the catalyst using pure steam, to yield a modified catalyst; and 3) adding the modified catalyst obtained in 2) to a conventional catalytic cracking reactor, injecting the bio-oil obtained in 1) to the conventional catalytic cracking reactor using a piston pump, and allowing the bio-oil to react under a weight hourly space velocity (WHSV) of between 6 and 15 h−1, a temperature of between 380 and 700° C., and a pressure between 0.1 and 0.8 megapascal.