Abstract: This paper introduces clinical experience of Prof. Xuan Guowei in treating acne caused by hyperactivity of fire due to yin deficiency by applying method of nourishing yin and clearing away heat. Prof. Xuan Guowei pointed out that the cause of the acne was the kidney yin deficiency， which resulted in the imbalance of yin and yang of kidney and the hyperactivity of ministerial fire， thus causing the blood heat in lung and stomach. The treating principal is nourishing yin to discharge fire and clearing lung and removing toxicity. Xiaocuo decoction made by the modification of Erzhi pills together with Zhibai Dihuang pills can be used to treat acne.