The application provides a medicine for treating the hyperplasia of mammary glands and a preparation method thereof. The medicine is prepared from the following medicines in parts by mass: 110 to 130 parts of Chinese thorowax root, 110 to 130 parts of membranous milkvetch root, 110 to 130 parts of turmeric root-tuber, 90 to 110 parts of dried human placenta, 110 to 130 parts of malt, 130 to 150 parts of Indian iphigenia bulb, 130 to 150 parts of ecklonia kurome okam, 150 to 170 parts of oyster, 90 to 110 parts of nutgrass galingale rhizome, 110 to 130 parts of epimedium herb and 110 to 130 parts of danshen root. The medicine combines the eleven medicines such as the Chinese thorowax root and the membranous milkvetch root, so that a synergistic effect is produced among the medicines, and thereby the medicine can nourish the liver and the kidney, benefit Qi and blood, invigorate the spleen and the stomach, remove stasis and phlegm, resolve cardiac depression, dredge collaterals to remove stasis, resolve hard lumps, promote blood circulation to diminish swelling, promote Qi circulation to relieve pain and increase antibodies without side effects, thus achieving the objective of effectively treating the hyperplasia of mammary glands.