Abstract:Severe pneumonia is a common critical illness in clinic. Physical and chemical factor damage, immune defense dysfunction, pathogenic microorganism invasion and other reasons can lead to the occurrence of severe pneumonia. In recent years, the effect of intestinal flora on the occurrence and development of severe pneumonia has gradually become a hot research topic. A large number of studies have shown that patients with severe pneumonia are often accompanied by the disorder of intestinal flora, and intestinal microecologics have a positive effect on the treatment of severe pneumonia. This article reviews the relationship between intestines and lungs and its main ways of action, the relationship between the imbalance of intestinal flora and pulmonary diseases, the changes of intestinal flora in patients with severe pneumonia and the application of intestinal microecological agents in the treatment of severe pneumonia.