Objective To explore the application value of early postoperative enteral eco-immune nutrition in the nutritional support treatment for intra-abdominal infection. Methods The prospective study was conducted. The clinicopathological data of 62 patients with intra-abdominal infection who were admitted to the 940 Hospital of the People′s Liberation Army Joint Service Support Force from February 2018 to December 2018 were collected. All patients were randomly divided into two groups by the envelope method with double-blind technique, including patients who began being given enteral eco-immune nutrition preparation at postoperative 24-48 hours in eco-immune group and patients who began being given simple enteral nutrition preparation at 24-48 hours in control group. Observation indicators: (1) analysis of immune function indices before treatment and after 7 days of treatment in the two groups; (2) postoperative conditions in the two groups; (3) follow-up. Follow-up using telephone interview was performed to detect complications and recurrence of infection up to May 2019. Measurement data with normal distribution were represented as Mean±SD, and intra-group comparison and comparison between groups were analyzed using the t test. Count data were represented as absolute numbers or percentages, and comparison between groups was analyzed using the chi-square test. Results Sixty-two patients were screened for eligibility, including 38 males and 24 females, aged (54±14)years, with the range of 22-81 years. There were 30 in the eco-immune group and 32 in the control group. (1) Analysis of immune function indices before treatment and after 7 days of treatment in the two groups: before treatment, the percentages of CD3+, CD4+, CD8+, ratio of CD4+ /CD8+, count of natural killer (NK) cells, levels of blood endotoxin and immunoglobulin A (IgA) for the eco-immune group were 61%±12%, 34%±5%, 28%±5%, 1.25±0.34, 17.26%±2.74%, (2.4±0.3)ng/L, and (1.7±0.5)g/L, versus 59%±11%, 33%±5%, 27%±4%, 1.27±0.36, 16.96%±2.99%, (2.5±0.5)ng/L, (1.8±0.5)g/L for the control group, respectively, there were no significant differences between the two groups (t=-0.563, -0.354, -0.987, 0.327, -0.462, 0.887, 0.991, P>0.05). After 7 days of treatment, the above indices for the eco-immune group were 62%±8%, 37%±6%, 27%±8%, 1.45±0.32, 22.63%±7.25%, (2.2±0.4)ng/L, and (2.3±0.4)g/L, versus 58%±8%, 32%±4%, 27%±6%, 1.26±0.22, 16.26%±2.10%, (2.7±0.6)ng/L, and (2.0±0.4)g/L for the control group, respectively, there were significant differences in the percentages of CD3+, CD4+, ratio of CD4+ /CD8+, count of NK cells, levels of blood endotoxin and IgA (t=-2.393, -4.336, -3.074, -5.338, 4.010, -3.155, P 0.05). In the eco-immune group, the percentage of CD4+, ratio of CD4+ /CD8+, count of NK cells, levels of blood endotoxin and IgA showed significant differences after 7 days of treatment (t=-2.899, -2.739, -4.385, 2.157, -5.788, P 0.05). In the control group, the percentage of CD8+ and level of IgA showed significant differences after 7 days of treatment (t=3.659, -2.258, P 0.05). (2) Postoperative conditions in the two groups: the time to first flatus and duration of postoperative hospital stay of the eco-immune group were (2.4±0.5)days and (8±4)days, respectively, versus (2.9±0.7)days and (11±7)days of the control group; there were significant differences in the above indices between the two groups (t=-3.017, -2.764, P<0.05). In the eco-immune group, the incidence of complication was 6.7%(2/30), including 1 case of wound infection, 1 case of pulmonary infection. In the control group, the incidence of complication was 31.2%(10/32), including 6 cases of wound infection, 2 cases of pulmonary infection, 1 case of intra-abdominal infection, and 1 case of systemic inflammatory response syndrome. There was a significant difference in the incidence of complication between the two groups (χ2=4.122, P<0.05). The patients with infection were recovered after corresponding systematic conservative treatments. (3) Follow-up: of the 62 patients, 46 were followed up for 3-9 months, with a median follow-up time of 6 months, including 26 in the eco-immune group and 20 in the control group. During the follow-up, no complication or infection recurred in the two groups. Conclusion Compared with simple enteral nutrition, early postoperative enteral eco-immune nutrition in the nutritional support treatment is safe and effective for patients with intra-abdominal infection, which can enhance the immune function of patients, shorten the recovery time of patients, and reduce the incidence of infection complications. Key words: Infection; Intra-abdominal infection; Nutritional support; Eco-immune nutrition; Enteral nutrition; Postoperative; Efficacy