Abstract: OBJECTIVE To observe the therapeutic effect of different extract (water, 50% ethanol and 95% ethanol) of Shuru Xiaokuai decoction on hyperplasia of mammary glands in rats, and to identify the extract with therapeutical effect. METHODS The model of hyperplasia of mammary glands was prepared in Wistar female rats. After oral administration of different extract (water, 50% ethanol and 95% ethanol) of Shuru Xiaokuai decoction, the pathologic changes of mammary gland were observed under microscope, and the morphologic changes of nipple in every group observed. RESULTS The aqueous extract at low, middle and high dosage had a significant therapeutic effect on hyperplasia of mammary gland in rats. Only extract of 50% ethanol at high dosage had therapeutic effect, and all of 95% ethanol extract had no therapeutic effect on hyperplasia of mammary gland in rats. CONCLUSION The active extract of Shuru Xiaokuai decoction on hyperplasia of mammary glands in rats were aqueous extract.