Abstract: Objective To study the effects of lactulose combined with probiotics on Intestinal Microecology in elderly patients with severe pneumonia. Methods One hundred and twenty elderly patients with severe pneumonia admitted to Beijing Shijitan Hospital Affiliated to Capital Medical University from January 2016 to January 2018 were divided into lactulose intervention group and combined intervention group. The lactulose intervention group was treated with Duphalac, and the combined intervention group was treated with BIFICO and Duphalac. Ke was treated with combination therapy. After one month of treatment, the changes of intestinal microecology, intestinal barrier function, white blood cell count and C-reactive protein expression were detected. The clinical indicators, total effective rate, pulmonary infection score and adverse reactions were observed and counted. Results The levels of lactobacillus, enterococcus, Enterobacter and digestive Streptococcus in the combined intervention group were significantly lower than those in the lactulose intervention group, and the levels of Bifidobacterium were higher than those in the lactulose intervention group (all P<0.05). The levels of diamine oxidase (DAO) and blood D-lactic acid in the combined intervention group were significantly lower than those in the lactulose intervention group (all P<0.05). WBC and CRP expression levels were significantly lower in the combined intervention group than in the lactulose intervention group (all P<0.05); the clinical observation indexes in the combined intervention group were better than those in the lactulose intervention group (all P<0.05); the pulmonary infection score in the combined intervention group was significantly lower than that in the lactulose intervention group (all P<0.05); and the total number of patients in the combined intervention group was significantly lower than that in the lactulose intervention group (P<0.05). The effective rate was significantly higher than that of lactulose intervention group,and the incidence of adverse reactions was significantly lower than that of lactulose intervention group (all P<0.05). Conclusion Lactofructose combined with probiotics can effectively improve the intestinal microenvironment and clinical symptoms of elderly patients with severe pneumonia, reduce the damage caused by antibiotics, and improve the quality of life of patients.