The invention belongs to the field of traditional Chinese medicines, and discloses a tincture for treating plasmacellular mastitis and a preparation method thereof. The tincture is prepared from the following raw materials: swimming crab meat, cortex moutan, lignum dalbergiae odoriferae, lamiophlomis rotate, rhodiola rosea, garden balsam seeds, portulaca oleracea, castor seeds, cryptotaenia japonica, towel gourd, Chinese prickly ash, semen phaseoli, hollyhock seeds, quisqualis indica, faeces leporis, radix ampelopsis, dragon bone, betel pepper leaves, calendula officinalis, halloysitum rubrum, melinis repens, sansevieria trifasciata, blue chamomile essential oil, laurocapram, squalane, menthol and an alcoholic solution with the mass fraction of 75%. The tincture provided by the invention is convenient to carry and use, shows good affinity and permeability with skin, can directly act on the breasts, so that the drugs can focus on the diseased part to be quickly absorbed by the human body by penetrating through the skin barrier; besides, the drugs supplement each other in the curative effect and mutually gain from each other, thereby having the effects of promoting blood circulation to remove blood stasis, clearing heat for detumescence, sterilizing, detoxifying, removing slough, promoting growth of tissue, relieving sensitivity and moisturizing, and being capable of effectively treating plasmacellular mastitis.