The invention relates to a method for extracting, separating and purifying an active component of Chinese herbal medicine, namely genistein from roots and stems of pigeon pea, and aims at providing a method for easily, safely, economically and effectively extracting, separating and purifying the high-purity genistein from roots and stems of the pigeon pea. The adopted technical proposal comprisesthat: fresh or dry roots and stems of the pigeon pea are used as raw materials, and by adopting the homogenate induction technique, the enzyme and acid induction technique, the solvent extraction technique, the ultrasonic oscillation flocculation technique, the negative pressure cavitation suspension solid extraction technique, the macroporous absorbent resin enriching technique, the positive phase silica gel medium-pressure column chromatography separation technique and the low-temperature crystallization and re-crystallization technique, the refined genistein is obtained, and the purity of the genistein reaches more than 95 percent. The method has the advantages of abundant and easily obtained raw materials, simple and convenient process, high yield and purity of the obtained genistein,suitability for industrialized production and high added value of products.