Objective To investigate the correlation between Patient-Generated Subjective Global Assessment (PG-SGA) and the index of body composition in nutritional assessment of patients with digestive tract cancer. Methods The nutritional status of 101 patients with digestive tract cancer were evaluated by Patient-Generated Subjective Global Assessment (PG-SGA), and in the meantime, the body composition was measured by multi-frequency bioelectrical impedance analysis, then take correlation analysis on the result. Results 65 cases were malnutrition, the rate is 64.36%. The incidence of gastric cancer patients with PG-SGA scores more than 4 was 76%, significantly higher than 52.95% of patients with colorectal cancer (P ＜ 0.05). Body weight, body mass index, body fat mass, body fat percentage, lean body mass, total body water, extracellular body water in malnutrition patients were lower than those in non- malnutrition patients (P ＜ 0.05), there was no significant difference in protein content, skeletal muscle mass, body cell mass, intracellular body water between the two groups (P ＞ 0.05). The correlation between PG-SGA score and body mass, BMI, body fat mass and body fat percentage was higher than other body composition indexes. Conclusions The incidence of malnutrition was high in digestive tract cancer patients especially in gastric cancer patients. The body weight , body fat mass ,lean body mass and other indexes were significantly decreased in the patients with malnutrition. There was a good correlation between PG-SGA score and body composition index, the combination of them can provide a more accurate assessment of preoperative nutritional status in order to provide the exact evidence for nutritional support.