This paper introduces the clinical experience of Cheng Yiqin in treating plasma cell mastitis. Cheng Yiqin considers that the root of its pathogenesis is disharmony of the liver and spleen, obstruction of mammary collaterals, and the branch is stagnation of qi, turbid phlegm, blood stasis and heat toxicity. In the treatment of the disease, He emphasizes that traditional Chinese medicine should be considered first with syndrome differentiation, combining Chinese medinine with Western medicine to obtain good therapeutic efficacy. He alse pays attention to the patients’ life style for prevention of the disease. When prescribing herbs to treat the disease, he stresses the methods of soothing the liver and clearing away heat, as well as regulating nutrient qi and drainig toxin. And one proven case is presented.