Methods: Choose from 6 to 2013-2013-12 gastric cancer patients, according to inclusion criteriaS to choose the objectS of study from the gastric cancer patients coming to our hospital 2013-06 to 2013-12 .The included patients will be randomly divided into two groups A and B, two groups of patients 4 days before operation begin to give parenteral nutrition: A: the control group of normal intravenous nutrition. B: the trial group,add Omega-3 Polyunsaturated Fatty Acids 0.2 g/kg to parenteral nutrition, no use on the day of surgery, postoperative 2 days continue to add Omega-3 Polyunsaturated Fatty Acids 0.2 g/kg. Detect and compare CRP、TNF-α、IL-1、IL-4、lL-6、 IL-8、lL-10 levels of two groups in days before parenteral nutrition and applicating 3rd day and postoperative 1st, 3rd, 5th,and detect liver function in preoperative and postoperative 2nd,5th,7th day. Record postoperative anal exhaust time, postoperative complications, postoperative hospital days, preoperative and postoperative body weight.Results: Trail group patients compared with the control group,Omega-3 Polyunsaturated Fatty Acids can reduce early postoperative inflammatory cytokines release, reduce the postoperative fever time, reduce the incidence of systemic inflammatory response syndrome, promote the recovery of gastrointestinal function, improve the nutritional state of patients, reduce infection and related complications after the surgery and reduce postoperative hospitalization days. Conclusions: Perioperative application of omega 3 PUFA can reduce the release of inflammatory cytokines, regulating cell and humoral immunity, reduce the postoperative fever time, reduce the local inflammation medium that inhibit the gastrointestinal peristalsis, promote the recovery of gastrointestinal function, improve the nutritional state of patients, thereby reducing the occurrence of postoperative infection and related complications, reduce postoperative hospitalization days.