A method for preparing 2,3,3,3-tetrafluoropropene, including: a) heating and vaporizing hydrogen fluoride and 1,1,2,3-tetrachloropropene (TCP), and introducing hydrogen fluoride and TCP to a first reactor for reaction in the presence of an A-type catalyst to yield a first product mixture including 2,3-dichloro-3,3-difluoropropene (“HCFO-1232xf”), where the mole ratio between hydrogen fluoride and TCP is between 5:1 and 60:1, the reaction temperature is between 200 and 500° C., and the space velocity is between 200 and 2000 h−1; b) preheating the first product mixture including HCFO-1232xf, introducing the first product mixture including HCFO-1232xf to a second reactor for reaction in the presence of a B-type catalyst to yield a second product mixture including HFO-1234yf, where the temperature of the preheated first product mixture including HCFO-1232xf is higher than the reaction temperature of the first reactor and lower than the reaction temperature of the second reactor.