Objective It was investigated the incidence of malnutrition in elderly patients with malignant tumor in our hospital, and further analyzed the correlation among malnutrition and different clinical factors. Methods PG-SGA was determined for the cancer inpatients in our hospital, then we analyzed the relativities among the age、stages、therapy、length of stay (LOS)、cost and other clinical factors. Results (1)The incidence of malnutrition was up to 67.9% in these 744 elderly inpatients; (2)Compared with non-gastrointestinal cancer patients, the incidence of malnutrition (81.9% vs 58.2%) and severe-malnutrition(40.5% vs 22.7%) increased significantly in patients with gastrointestinal cancer (P<0.001). (3)Correlation analysis of nutritional status and clinical factors in elderly patients with gastrointestinal malignant tumor: ①According to the Stratification by using age factors, malnutrition rates were no significant difference in patients (P=0.462); ②Different stages (TNM) didn’t show any difference on nutritional status (P=0.595), The malnutrition incidence of Stage Ⅰ+Ⅱ patients was 79.3% (88/111), and Stage Ⅲwas 88.8% (103/116), Stage Ⅳ was 87.5% (42/48); ③ Compared with chemotherapy (236 cases) , elderly cancer patients with surgery (37cases) had a lower rate of malnutrition (86.0% vs 64.9%, P=0.001); ④The median costs of hospitalization for patients with severe malnutrition (20672.70 yuan) were significantly higher than those without malnutrition(12420.15 yuan) or mild / moderate malnutrition (15384.20 yuan), P=0.004, and there was no significant difference in between the latter; ⑤The median length of stay for patients with severe malnutrition (14.00 days) were significantly higher than those without malnutrition (6.50 days) or mild / moderate malnutrition (7.50 days), P=0.002, and there was no significant difference in between the latter. Conclusion: ①Malnutrition is common in elderly patients with malignant tumors, especially in gastrointestinal cancers; ②The elderly cancer patients with severe malnutrition will significantly increase the cost of hospitalization and the length of stay; ③Different treatments have different effects on nutritional status, so we should judge and weigh the advantages and disadvantages and choose the right treatment; ④We should pay more attention to the nutritional status of elderly cancer patients, and it’s important early screening and timely intervention.