Objective To explore the effect of individualized nutritional therapy on nutritional status of patients with nutritional risk in the perioperative period of the digestive system operation. Methods This study was a prospective, randomized, controlled clinical trial. Patients undergoing elective digestive surgery were screened for nutritional risk. And 231 patients who had nutritional risk and signed informed consent were randomized into study group (n=115) and control group (n=116). Individualized and non-individualized nutritional treatments were given for 15 d (5 d before surgery and 9 d after surgery) in two groups. The baseline data were collected. At admission, and on day 5, 9 and 15 after nutrition treatment, venous blood samples were collected, and relevant indicators, such as the body mass index (BMI), serum total protein, albumin, prealbumin, blood glucose, total cholesterol, triglyceride, lymphocyte count and white blood cell count, were measured. Results At the end of the trial, 217 patients were collected from the study group (n=112) and control group (n=105). Fourteen patients (6.1%) withdrew from the study. In the study group, the levels of serum total protein, albumin and prealbumin were first increased, then decreased, and then increased again (P<0.05); the lymphocyte count and white blood cell count were first decreased and then increased (P<0.05); all were within the normal range. In the control group, serum albumin level was first decreased and then increased (P<0.05); serum prealbumin level and lymphocyte count were increased, then decreased, and then increased again (P<0.05); all were within the normal range; there were no significant differences in the other indicators (P>0.05). Serum total protein and albumin levels were significantly higher in the study group than those in the control group (P<0.05). White blood cell count was lower in the study group than that in the control group on day one before surgery (P<0.05), but white blood cell count was higher in the study group than that in the control group on day 9 after surgery (P<0.05). There was no significant difference in the other indexes between the two groups (P>0.05). The duration of nutrition treatment was not related to nutritional or immune indexes (P>0.05). Conclusion Individualized nutritional therapy can improve the nutritional status of patients with nutritional risks in the perioperative period of the digestive system operation.