Abstract: Objective To explore the influence of parenteral nutrition (PN)supportive therapy on the nutritional status and immune function in patients with advanced gastrointestinal tu-mor in peri-chemotherapy period.Methods 90 patients with advanced gastrointestinal tumor were randomly divided into control group and observation group.Efficacy was compared between two groups by detecting the changes of various nutritional and immune indexes before and after chemotherapy.Results There were no significant differences of the nutritional and immune func-tion indexes between two groups before chemotherapy and after the first-second cycle of chemothera-py.All nutritional and immune function indexes after the third cycle of chemotherapy in the obser-vation group were significantly better than those in the control group.The incidence rate of compli-cations such as leucopenia,thrombocytopenia,nausea,vomiting and diarrhea in the observation group was significantly lower than the control group.Conclusion PN supportive therapy can not only ameliorate the nutritional status and immune function of patients with advanced gastrointestinal tumor,but also alleviate the chemotherapy-induced adverse reactions,so it is very important for safety in peri-chemotherapy period.