Objective:To investigate the effects of enteral immunonutrition on the intestinal barrier function and immune function in patients with severe pneumonia.Methods:Ninety patients with severe pneumonia were randomly divided into experimental group (n =45) and control group (n =45).All patients were received conventional therapy.In addition,patients in experimental group were given enteral immunonutrition,while patients in control group were given regular enteral nutrition.The changes of general conditions,intestinal barrier function index and immune function index were determined before treatment,on day 5 and 10 after treatment.The time of invasive mechanical ventilation,APACHE Ⅱ score and clinical effects of two groups were determined on day 10 after treatment.Results:Compared with those before treatment,in both groups,body temperature,respiration,heart rate,white blood cell count were all significantly decreased on day 5 and 10 after treatment (P ＜ 0.05).The above parameters were significantly lower in experimental group than control group on day 10 after treatment (P ＜ 0.05).The levels of serum ET,DAO were significantly decreased on day 5 and 10 after treatment in two groups compared with those before treatment (P ＜ 0.05),and these parameters were significantly lower in experimental group than control group(P ＜0.05).The number of CD3 and CD4 positive cell and the ratio of CD4 +/CD8 + were significantly increased on day 5 and 10 after treatment in two groups when compared with those before treatment (P ＜ 0.05),and these parameters were higher in experimental group than those in control group(P ＜ 0.05).The time of invasive mechanical ventilation,APACHE Ⅱ score were lower in experimental group than those in control group on day 10 after treatment (P ＜ 0.05).The rate of clinical response were higher in the experimental group than that in the control group on day 10 after treatment (P ＜ 0.05).Conclusion:Enteral immunonutrition is more effective in protecting the intestinal barrier function,improving the immune status,enhancing the immunity,reducing the time of invasive mechanical ventilation,and achieving the clinical effects of patients with severe pneumonia.