This paper discussed the medical achievements on the differentiation and treatment of phlegm and fluid retention before Tang Dynasty. By studying the famous medical works before Tang Dynasty,it found that,the definition of phlegm and fluid retention was not clear in Inner Canon of Huangdi(Huangdi Neijing),which put forward the theory of water-fluid metabolism in zang-fu viscera and prescription rules of nature and flavour compatibility. The differentiation and treatment of phlegm and fluid retention were systematically summarized in Treatise on Cold Pathogenic and Miscellaneous Diseases(Shanghan Zabing Lun),which deeply involved principle-method-recipe-medicines. In General Treatise on Causes and Manifestations of All Diseases(Zhu Bing Yuan Hou Lun),the etiology and pathogenesis of phlegm and fluid retention in human body were systematically summarized. As to Recipes Worth A Thousand Gold(Qianjin Fang)and Arcane Essentials from the Imperial Library(Waitai Miyao Fang),the experience of medicines and prescriptions in the differentiation and treatment of phlegm and fluid retention before Tang Dynasty were widely collected,which enriched the academic system of differentiation and treatment of phlegm and fluid retention. Zhang Zhongjing created the systems of principle-method-recipe-medicines for differentiation and treatment of phlegm and fluid retention,which reached the highest level. Therefore,for the summary of medical achievements on the differentiation and treatment of phlegm and fluid retention before Tang Dynasty,it was necessary to perform the comparative study based on Zhongjing’s theory.