The paper studied the extraction technology of isoflavones from the defatted soybean meal that was pre-treated by microwave. Through the orthogonal experiment (L9 (34)), the optimal microwave treatment time, alcohol concentration in the alcohol aqueous solution, the ratio of solvent to the defatted soybean, temperature and the extraction time were 15s, 65%, 1/15, 45min and 50℃, respectively, under which the extracting rate was 0.78%. The microwave treatment can enhance the extracting rate of isoflavones from soybean.