The invention discloses an extraction method of Diosbulbin B, which comprises the following steps: carrying out reflux extraction on airpotato yam acetone, and concentrating the extracting solution until no acetone smell emits, thereby obtaining an extract; mixing the extract and silica gel, adding petroleum ether for extraction, drying filter residues by evaporation, adding chloroform for extraction, and drying the extracting solution by evaporation, thereby obtaining a chloroform part; mixing the chloroform part and silica gel, passing the mixture through columns, eluting with a mixed solution of chloroform and methanol in the volume ratio of 98:2, and collecting the eluent at multiple sections; recovering the solvent from the eluent, dissolving in acetone, crystallizing to obtain a crystal, passing the filtrate through columns, and eluting with a mixed solution of chloroform and methanol in the volume ratio of 99:1; and recovering the solvent from the eluent, dissolving in acetone, crystallizing, and merging the crystals to obtain the Diosbulbin B. In the invention, by selecting the extraction process and the eluents, the Diosbulbin B can be extracted, and the obtained extract does not contain other substances, thus further separation and purification are not needed. The method is relatively simple to operate, can be used for effectively extracting the Diosbulbin B, and has important meanings for further research on pharmacology and drug effects of the Diosbulbin B.