Objective To explore the effectiveness of applying nutritional intervention based on the Prognostic Nutritional Index assessment to patients with colorectal cancer. Methods In the prospective comparative design, the first batch of 64 patients with colo-rectal cancer were selected as the control group, who received routine nutrition intervention, and the second batch of 56 patients with colorectal cancer as the intervention group, who was given nutrition support intervention based on the Prognosis Nutrition Index assessment. Results There was significant difference in the distribution of postoperative nutritional status between the two groups (P＜0.05,P＜0.01).The time to first passage of flatus, and first bowel movement, the time to first bite of solid food and the time to return of bowel sounds in the intervention group were significantly shorter than those in the control group; the incidence rates of pulmonary infection and wound infection in the former group were significantly lower than those in the latter group (P＜0.05,P＜0.01). Conclusion Nutritional intervention based on the Prognostic Nutritional Index assessment can effectively improve nutritional status of patients, reduce postoperative complications and promote postoperative recovery.