Objective:To investigate the effect of oral administration of vitamin D3 on intestinal barrier function in patients after gastric cancer surgery,and to provide a reference for perioperative nutritional therapy in patients with gastric cancer.Methods:The conve-nience sampling method was used to select 80 patients with gastric cancer who were admitted to Department of Gastrointestinal Surgery in a grade A tertiary hospital in Xiamen,China,from June 2021 to May 2023,and the patients were divided into intervention group and control group using a random number table.The patients in the intervention group were given oral administration of vitamin D3 800 IU/d for 14 consecutive days before surgery.ELISA was used to measure the serum levels of 25-hydroxyvitamin D3[25(OH)D3],intestinal barrier indicators(D-lactate,Zonulin),and inflammatory indicators(C-reactive protein,interleukin-6)within 24 hours after admis-sion and on days 1,4,and 7 after surgery,and the changes in these indicators were compared between the two groups.Results:A total of 71 patients were enrolled finally,with 34 in the intervention group and 37 in the control group.On days 1,4,and 7 after surgery,the intervention group had a significantly lower level of D-lactate than the control group(F=3.978,P=0.026;F=9.649,P=0.005;F=4.389,P=0.021).On day 4 after surgery,the intervention group had a significantly lower level of Zonulin than the control group(F=3.198,P=0.035).Conclusion:Oral administration of vitamin D3 before surgery may accelerate the recovery of intestinal barrier function in pa-tients with gastric cancer.