Objective To explore the effect of ω-3 fish oil fat emulsion on the inflammatory response and serum albumin (ALB), total protein (TP) and prealbumin (PA) levels in the early recovery stage of postoperative patients with gastrointestinal tumor. Methods A total of 96 postoperative patients of gastrointestinal tumor admitted to the Fourth People's Hospital of Yixing from March 2019 to January 2021 were selected as the research objects, and they were divided into the control group and the observation group according to the random number table method, with 48 cases in each group. Patients in the control group received parenteral nutrition support, and patients in the observation group were treated with ω-3 fish oil fat emulsion on the basis of the control group, Patients in the two groups were treated continuously for 9 days. The nutritional indicators and serum C-reactive protein (CRP), interleukin-6 (IL-6), interleukin-10 (IL-10) and tumor necrosis factor-α (TNF-α)level and neutrophil count, compared the incidence of postoperative complications of patients between the two groups. Results Serum TP levels of patients in the observation group gradually increased from 3~9 d after operation, the serum PA levels of patients in the two groups decreased first and then increased, the serum TP levels of patients in the observation group were higher than those in the control group at the 6, 9 d after operation, the serum PA level of of patients in the observation group was higher than that of the control group at 3, 6, and 9 d after operation; the serum IL-6 levels of patients in the observation group and the serum TNF-α levels, serum CRP levels, and neutrophil counts of patients in the two groups gradually decreased 3~9 d after operation, the serum IL-6 level of patients in the control group increased first and then decreased, and the observation group was lower than the control group at each time point; the serum IL-10 levels of patients in the two groups decreased first and then increased 3~9 d after operation, and the observation group was higher than the control group at each time point; the incidence of systemic inflammatory response syndrome (SIRS) of patients in the observation group was 10.42%, which was significantly lower than that 27.08% in the control group, and the infection rate of patients in the observation group was 6.25%, which was significantly lower than that 20.83% in the control group (all P <0.05). Conclusion The addition of ω-3 fish oil fat emulsion on the basis of parenteral nutrition support of postoperative patients with gastrointestinal tumor can effectively promote the recovery of the patients’ nutritional status, inhibit the body's inflammatory response, and can reduce the occurrence of complications, and which has higher safety.