Objective To observe the effects of olive oil-based lipid emulsion in parenteral nutrition on the immune function and postoperative recovery of patients with colorectal cancer. Methods 80 cases of colorectal cancer were randomized into two groups after critical abdominal surgery. Parenteral nutrition with structure lipid emulsion was processed in both groups after surgery.Treatment group was given olive oil-based lipid emulsion (ClinOleic). Control group was added medium and long chain fat emulsion. Effects on the incidence of postoperative complications, anal exhaust time, intravenous nutrition, length of hospital stay, and the levels of C-reaction protein (CRP) were compared. The effect of postoperative intestinal function recovery and immune function improvement were investigated and the possible mechanism was explored. Results There was no statistical difference between the two groups. The incidences on complications (sore throat, nausea and vomiting, reposition gastrointestinal decompression tube, incision infection, pulmonary infection, intestinal obstruction, anastomotic leakage) have no statistical differences (χ 2 =4.512, P>4.512). In the treatment group, the immunological function of the patients were significantly improved, and the C-reactive protein decreased by 67.470-43.786 significantly (t=4.290, P<0.001). The time of anal venting, intravenous nutrition and postoperative hospitalization of treatment group were all shorter than the control group (P<0.05). Conclusions Olive oil-based lipid emulsion can significantly improve the immune function and accelerate the postoperative recovery of colorectal cancer.