Abstract： To introduce the clinical experience of Prof. GAO Xiangfu in treating dermatomyositis by stages. Prof. GAO believes that dermatomyositis belongs to the category of skin impediment in Chinese medicine，and its key pathogenesis is the occurrence of deficiency and depletion of the lung and spleen and the internal invasion of damp-heat，toxin and stasis. According to the bias of healthy qi and pathogenic qi and the root and branch，as well as the urgency of the disease，GAO put forwards the treatment principle of treating by stages. In the acute phase，the treatment is to clear heat and resolve toxins，invigorate blood and unblock the collaterals， and clear heat and drain dampness， and mainly remove pathogenic factors； the prescriptions should be modified Simiao Yong'an Tang combined with Maxing Shigan Tang. In the delay phase， the treatment is to supplement the spleen and boost the lung， clear heat and drain dampness， harmonize blood and protect collaterals，and mainly consolidate and protect healthy qi，and eliminate the remaining pathogenic qi；the prescriptions should be modified Huangqi Guizhi Wuwu Tang combined with Simiao Yong'an Tang. GAO's medication according to different syndromes is of great characteristics： to purge the internal and external dampness by Ephedrae Herba and Atractylodis Macrocephalae Rhizoma purging the interior and exteroior；to treat skin ulcer by internal application of Chinese herbs roasting pus and generating skin；to treat concomitant interstitial lung disease from lung abscess；to prevent and treat tumors by using Smilacis Glabrae Rhizoma，Sophorae Flavescentis Radix，Scutellariae Radix and Actinidiae Chinesis Radix.