Objective To compare the application of global leader′s initiative on malnutrition (GLIM) and patient⁃generated subjective global assessment (PG⁃SGA) in diagnosing malnutrition among cancer patients. Methods From January 2019 to December 2020, 266 cancer patients were randomly selected from 416 Hospital of nuclear industry and assessed the incidence of malnutrition by GLIM criteria and PG⁃SGA respectively, and the consistency of two methods in diagnosing malnutrition was compared. Results ①The NRS 2002 score of cancer patients was (3.08±1.04), and the incidence of nutritional risk was 52.6% (140/266). There were significant differences of incidence of nutritional risk among different age groups, tumor types and tumor stages (P<0.05). ②Among the five phenotypes of GLIM, the incidence of weight loss, low BMI, muscle loss, decreased food intake/digestive dysfunction and disease/inflammatory burden were 44.0%, 17.3%, 41.7%, 69.2% and 38.7% respectively. The incidence rate of malnutrition assessed by GLIM criteria was 36.8%. There were significant differences of incidence of malnutrition among different age groups, tumor types and tumor stages (P<0.05). ③113 cases of cancer patients were diagnosed malnutrition by PG⁃SGA with the incidence rate 42.5%. There were significant differences of malnutrition incidence among different age groups, tumor types and tumor stages (P<0.05). The older age, the higher incidence of malnutrition, digestive system tumors were higher than other tumors, and the higher tumor stage, the higher incidence of malnutrition. ④The consistency of GLIM and PG⁃SGA was good to diagnose malnutrition stratified according to the general situation of tumor patients. A total of 90 cases of cancer patients was diagnosed malnutrition by GLIM and PG⁃SGA. The two methods were consistent in diagnosing malnutrition with the Kappa value 0.76. Conclusion The incidence of malnutrition and nutritional risk is high among cancer patients. There is a good consistency between GLIM and PG⁃SGA in diagnosing malnutrition, but more prospective studies are needed to confirm it.