Objective To explore the postoperative influence of intra-abdominal implantation of sustained-releasing 5fluorouracil on the hepato-renal function, immune function, nutritional state and complications in patients with gastric and colorectal cancer. Methods Sixty-five patients with gastric or colorectal cancer were included into this study from January to June 2009. The patients (35 cases of gastric cancer, 18 cases of colon cancer and 12 cases of rectal cancer) were randomly divided into experimental group (n=25) and control group (n=40). In experimental group, 400 mg sustained-releasing 5-fluorouracil was used. Blood samples were gained before operation, the second day and the seventh day after operation to examine the indexes of hepato-renal function, immune function and nutritional state. Complications， venting time and length of stay after operation were also recorded. Results There was no statistical significance for distribution of tumor stages and patients’ gender between experimental group and control group (Pgt;0.05). Preoperative indexes of hepato-renal function, immune function and nutritional state were also not reached statistical significance between two groups (Pgt;0.05). Compared with control group, the indexes of total protein and transferrin were decreased and urea nitrogen and IgM were increased in the second day after operation in experimental group (Plt;0.05). The number of lymphocyte was increased, while CD4, Alb, total protein and IgA were decreased in the seventh day after operation in experimental group, respectively. The time of passage of gas of experimental group was longer than that of control group (Plt;0.05).Conclusion Intra-abdominal implantation of sustained-releasing 5-fluorouracil is safe and feasible, which does not increase the complications and the time of length stay after operation. However, there is a little influence on immune function and gastrointestinal function after operation for intra-abdominal implantation of sustained-releasing 5-fluorouracil.