Objective To evaluate the use of the patient-generated subjective global assessment (PG-SGA) for the assessment of nutritional status in patients with gastrointestinal tumors. Methods 304 patients hospitalized in Huizhou Municipal Central Hospital from May 2015 to May 2016 were enrolled. The diagnosis with gastrointestinal tumors was confirmed by pathological examination and patients received chemotherapy/radiotherapy or surgery or treatment for complication. The patients were interviewed by a trained surgeon using PG-SGA within 24 hours after admission. PG-SGA score ≥ 4 indicated malnutrition. PG-SGA score ≥ 9 indicated serious malnutrition. Results 304 patients participated in this study, 80.6% of the patients’ had PG-SGA score ≥ 4, 34.2% of the patients’ had PG-SGA score ≥ 9. The incidence of malnutrition in the patients received surgery is higher than patients received chemotherapy/radiotherapy, the incidence of malnutrition in the patients with upper gastrointestinal cancer is higher than the patients with lower gastrointestinal cancer, the incidence of malnutrition in the patients of bearing cancer is higher than patients of unbearing cancer. The difference are significant. The correlation between the scores of PG-SGA and the TNM pathological stage is positive; the later stage, the more scores of PG-SGA assessment. The length of hospital stay and the hospitalization costs between patients with and without malnutrition are significant different. Conclusions The incidence of malnutrition in the patients of gastrointestinal tumors is high, we should pay attention to the nutrition assessment and nutrition therapy for these patients. PG-SGA is an appreciated tool for nutritional assessment for patients with gastrointestinal tumors. It can predict the clinical stage, the length of hospital stay and the hospitalization costs. Remove the tumor from the patient is an effect way to improve the nutritional status of the patients with gastrointestinal tumors.