An abnormal microenvironment which is not fit for the living of normal cells is induced and maintained due to rapid growth, abnormal energy metabolism and self-regulation of specific proteins of the tumor cells. At the same time, the abnormal microenvironment is the guarantee of the neoplastic transformation, proliferation, invasion and metastasis of tumor cells. The microenvironment mainly consists of interstitial cells and their components. There are correlations between the physiological role of body fluid and the physiological functions of microenvironment. Phlegm is the product of abnormal body fluid metabolism. So to discuss the correlations of them may contribute to clarifying the material base of phlegm and will further give new insight for integrated traditional Chinese and Western medicine in cancer research.