Cachexia is a complex metabolic syndrome characterized by loss of skeletal muscle (with or without loss of fat mass), which affects the majority of late stage cancer patients. Cancer cachexia often seriously affects the treatment efficacy and increases the toxicity by chemotherapy and radiotherapy, further increasing mortality and leading to poor prognosis for cancer patients. The mechanism of cancer cachexia on metastasis have not been understood completely, which may be associated with inflammation, hypoxia, decreased expression of leptin and the release of proangiogenic factors in cancer patients with cachexia. The pathological and physiological characteristics of cachexia are complicated, and cancer cachexia is associated with poor response of therapy without standard treatment. There remains an urgency to study the pathophysiology of cachexia and the impact on metastasis to guide early nutrition screening and assessment, to identify the diagnosis of cachexia and to evaluate the stage and grade of cachexia. Also,   it is useful to predict and treat cachexia positively and effectively, to decrease the metastatic rate of tumor and improving quality of life. This review will summarize the effect of cancer cachexia on metastasis by exploring the pathophysiology of cachexia and the pathogeneses of cachexia on metastasis, to provide important basis on the treatment of cancer cachexia and metastasis.