Body composition refers to the proportion of various body components muscle adipose tissue skeletal muscle tissue etc. which is a symbol to measure the distribution of tissues in the body one of which can make a great difference on body health or disease. 40%-80% of tumor patients are prone to be complicated with malnutrition and even progress to cachexia. The occurrence of malnutrition seriously affects the survival and prognosis of tumor patients and reduces their tolerance and sensitivity to radiotherapy and chemotherapy. During the occurrence development and treatment of tumors the relevant body composition indexes often vary with the changes of patients' nutritional status the degree of malignancy of the disease the rate of progression and the adjustment of therapy. Therefore human composition as an important monitoring index is related to the survival prognosis analysis and drug toxicity evaluation of patients. Well body composition analysis is an important way to assess the nutritional status of tumor patients and predict their quality of life early which is helpful to make individualized treatment according to the current status of patients. With the widespread use of noninvasive body composition measurements body composition analysis has unique advantages in diagnosis and evaluation of nutritional status of cancer patients prediction of efficacy and toxicity of anti - tumor drugs as well as survival and prognosis. A number of clinical trials related to body composition in cancer patients have been conducted in this article we provide an overview of the clinical application of body composition analysis in cancer patients.