The invention discloses a medicine for assisting in treating a breast cancer and a preparation method of the medicine. The medicine comprises the following raw materials in parts by weight: 25-60 parts of centipede extract, 12-35 parts of angelica sinensis, 18-29 parts of selfheal, 12-30 parts of akebiaquinata, 11-28 parts of ormosia, 8-19 parts of codonopsis pilosula, 7-22 parts of glycyrrhiza uralensis, 6-21 parts of rhubarb, 8-22 parts of astragalus mongholicus, 9-23 parts of ginseng, 7-20 parts of nightshade and 6-19 parts of oolong tea. The prepared medicine for assisting in treating thebreast cancer can assist in western medicine treatment of the breast cancer, particularly can effectively eliminate or inhibit tumor development for late-stage patients incapable of undergoing surgery, chemotherapy and radiotherapy, improves clinical symptoms of the patients, reduces toxic and side effects of the chemotherapy and the radiotherapy, overcomes multidrug resistance of tumor cells, regulates immunologic mechanisms of bodies, improves curative effects of the surgery, the chemotherapy and the radiotherapy, improves the life quality of the patients, and prolongs the life time.