Abstract: Cachexia is a serious disease worldwide, with an increasing incidence year by year, often accompanied by a variety of chronic diseases.Among them, cancer cachexia has the highest incidence and is a common complication of various advanced cancer patients.About 60%-80% of advanced cancer patients may present with cachexia, and about 20% of patients with cancer die with cachexia.Therefore, the accurate clinical diagnosis of cancer cachexia and the development of effective interventions are of great importance for the long-term survival of patients with cancer.Based on the analysis, discussion and summary of relevant study evidence and clinical experience in screening, diagnosis, evaluation and treatment of cancer cachexia, the Chinese Society for Nutritional Oncology formulated the Guidelines for Clinical Diagnosis and Treatment of Cancer Cachexia (2020 Version) for clinicians'reference.