Tumor nutrition is a new discipline that applies nutrition methods and theories to prevent and treat tumors. Malignant tumor patients are at high risk of malnutrition. Malnutrition will affect the treatment, prognosis and survival time of tumor patients. Therefore, a dual diagnosis of tumor and nutrition is required for tumor patients when they are admitted to hospital. As a highly sensitive and highly specific detection method, mass spectrometry can be used for accurate monitoring of various indicators in the human body, and provide accurate and rich diagnosis and treatment information for tumor patients from the perspective of nutrition. In this paper, the application of mass spectrometry technology in tumor nutrition diagnosis and treatment was reviewed. The applications of liquid chromatography⁃triple quadrupole mass spectrometry, time⁃of⁃flight mass spectrometry, and inductively coupled plasma mass spectrometry in tumor nutrition diagnosis and treatment were summarized. This paper reviewed the accurate detection of vitamins, trace elements, glucocorticoids, therapeutic drugs and other indicators in the human body by mass spectrometry. More accurate data support will be provided to nutritional support for clinical tumor patients.