Objective This study aims to investigate the prevalence of sarcopenia specifically in Chinese patients with malignant tumors. Method A total of 61 627 patients with 19 types of malignant tumors from 86 grade-A hospitals from July 2013 to December 2023 were included in the INSCOC database of the Chinese Tumor Nutrition Cohort Study. The diagnostic criteria for sarcopenia provided by the Asian Working Group on Sarcopenia AWGS in 2019 were used. Chi-square test or Fisher exact test was used to compare the prevalence of sarcopenia in patients with different population characteristics. Result The prevalence of sarcopenia in cancer patients was 18. 1%. The prevalence of sarcopenia varied with tumor type TNM stage age gender administrative area and treatment. The prevalence of sarcopenia was higher in patients with digestive system cancers and the highest prevalence was found in patients with pancreatic cancer 32. 4% 311 / 961 . The prevalence of sarcopenia increased with the increase of TNM stage P< 0. 05 . The prevalence of sarcopenia was the highest in patients over 70 years old 34. 7% 3510 / 10 129 . The prevalence of sarcopenia in female cancer patients was higher than that in male patients 16. 1% 5544 / 34 381 vs 20. 7% 5631 / 27 246 P<0. 05 . The lowest prevalence was found in the Northeast region 14. 7% 2398 / 16 300 . Patients who received surgical treatment had the highest prevalence 22. 1% 1635 / 7412 . In addition in some tumor types there were significant differences in the prevalence of sarcopenia among patients with different medical insurance types occupation education level ethnicity and place of residence. Patients with low education level and farmers had a higher risk of sarcopenia. Conclusion This study is the first to report the incidence of sarcopenia in tumor patients on a large scale with a prevalence of 18%. Patients with digestive system cancers elderly farmers low education level and advanced tumor are high risk groups for sarcopenia.