The invention belongs to the technical field of preparation of biomass chemicals and discloses a method for preparing furfural from corncobs through microwave assisted SnCl4 catalysis. The preparation method comprises steps as follows: degreased corncobs, a catalyst SnCl4 and water are added to a reactor and evenly mixed ultrasonically, then nitrogen is introduced at the microwave power of 400-600 W for oxygen removal, the mixture is heated by microwaves to the temperature of 160-190 DEG C for a reaction for 0-50 min, reaction products are separated and purified, and a product, namely, the furfural, is obtained. According to the method, the SnCl4 is used as the catalyst, the production of the furfural is highly selective, the catalytic efficiency is high, the environment-friendly effect is realized, corrosion is small, and the technological process is more environment-friendly; the reaction rate and the energy utilization rate are increased through microwave assisted heating, so that the reaction time is shortened, and the yield of the furfural is increased.