Xiao Qinglong Decoction stemmed from the theory of Treatise on Cold Pathogenic and Miscellaneous Diseases，which is a classical prescription with definite curative effect and widely used. Based on the review of the medical records in the past dynasties，combined with ancient medical records，modern research and clinical application，this paper discusses the characteristics of the treatment and prescription of Xiao Qinglong Decoction. It is believed that “yin” xie (pathogenic fluid) is usually the key point of pathogenesis，and the treatment of pathogenic fluid is the intention of Xiao Qinglong Decoction. If confined to “outside cold with inner fluid”，we will not make the best use of it.