The invention belongs to the field of traditional Chinese medicines, and discloses a plaster for treating hyperplasia of mammary glands and a preparation method thereof. The plaster is prepared from the following raw materials: common lamiophlomis, myrrh, leech, motherwort herb, diverse wormwood herb, nardostachyos root and rhizome, fruit of kwangsi dutchmanspipe, thin-petiole grass fern, root or stem of yellow angledtwig magnoliavine, leaf of corkleaf snowbell, oriental stephania root, dried toad, griffith condorvine, pangolin scales, prepared jackinthepulpit tuber, clausena emarginata, marmot bone, all grass of serrulate clearweed, manyprickle acanthopanax root, alysicarpus vaginalis, costus root, villous amomum fruit, licorice root, laurocapram, squalane, propolis, menthol, olive oil, chamomile essential oil, and isobutyl dicyanoacrylate. The plaster disclosed by the invention has very good affinity and permeability with skin, and can promote blood circulation, can enable medicines to quickly pass through a skin barrier, and can promote absorption of the medicines and bring the medicines into play to ensure that the medicines act on a breast directly, and reach lesions directly to achieve the effects of improving breast blood circulation, activating blood circulation to remove blood stases, regulating the flow of Qi to alleviate pain, reducing swelling and resolving mass, clearing and activating channels and collaterals, so that the plaster can obviously relieve breast pain symptoms and improve the state of glandular hypertrophy so as to treat hyperplasia of mammary glands.