Tumor seriously endangers human life and health. The nutritional status of tumor patients is closely related to various clinical outcomes of tumor diseases. Due to multiple factors such as emotion, tumor itself and anti⁃tumor treatment, it is easy to lead to insufficient intake of tumor patients, nutritional risk, and then malnutrition. Therefore, scientific nutritional treatment is needed for tumor patients. Oral nutritional supplements(ONS), as a method of enteral nutrition, it is the most feasible and convenient medical nutrition treatment for tumor patients, and has high⁃level evidence support. It has been recommended as the preferred application way of enteral nutrition for tumor patients by many guidelines. ONS is one of the important ways of nutritional intervention for cancer patients. Whether the patient is in the perioperative period, during radiotherapy and chemotherapy, and any tumor disease stage such as cachexia or end⁃stage tumor, ONS is suitable for patients with substandard nutritional intake. Choosing scientific and reasonable preparations, appropriate taking methods and perseverance will certainly play a role in improving the nutritional status of patients, helping patients better complete anti⁃tumor treatment, reducing complications, improving the quality of life of tumor patients and optimizing health economic indicators. This paper will review the progress of clinical application of ONS in tumor patients.