Cancer cachexia is a common consequence of advanced cancer. It is a multi-factorial syn- drome defined by an ongoing loss of skeletal muscle mass with or without loss of fat mass. Patients with severe muscle wasting usually have poor survival outcome, more treatment-related toxicities and post-operative complications. However, the definition, diagnostic criteria and clas­sification of cancer cachexia are still unclear. This article presents the most recent information of cancer cachexia, including definition, diagnostic criteria, mechanism, classification, assessment, treatment and prognostic indicator.