Abstract: Body composition is an important reference for evaluating nutritional status of cancer patients. We summarized the various methods of body composition assessment and its clinical applications in oncology. CT and MRI are the current gold standard in body composition evaluation with its high spatial and contrast resolution. Body composition can be used to predict chemotherapy tolerance; Nutrition evaluation based on body composition such as visceral obesity, sarcopenia and sarcopenia obesity are considered to be adverse prognostic factors in cancer patients. Body composition may be a significant predictor of treatment toxicities and prognosis, but its clinical application needs multidisciplinary cooperation and more well-designed prospective clinical trials.