The invention discloses a method for synthesizing a dihydrofuran compound containing a 1, 3-indandione spiro skeleton as shown in a formula III by using a micro-channel reaction device, which comprises the following steps: by using a 2-benzylidene-1, 3-indandione compound I and a benzoyl ethyl acetate compound II as reaction raw materials, carrying out continuous reaction by using the micro-channel reaction device to prepare the dihydrofuran compound containing a 1, 3-indandione spiro skeleton. The micro-channel reaction device comprises a feeding pump, a micro-mixer and a micro-reactor whichare sequentially connected through a pipeline. Compared with the prior art, the new dihydrofuran containing the 1, 3-indandione spiro skeleton is prepared by taking the 2benzylidene 1, 3-indandione compound as the substrate for the first time, and the method avoids multi-component reaction, uses a non-metal catalyst and a low-toxicity solvent, and is a quick, efficient, green and environment-friendly synthetic product, wherein R1 is selected from halogenated benzene, C1-C4 alkyl benzene, C1-C4 alkoxy benzene, nitrobenzene, furan or naphthalene, and R2 is selected from halogenated benzene, C1-C4 alkyl benzene, C1-C4 alkoxy benzene, nitrobenzene, furan, thiophene, pyridyl or naphthalene.