Abstract: In recent years， with the breakthrough of life science and emerging developments in microbiome research， a new concept has been referred to as the "lung-gut axis". To some extent， it coincides with TCM theory of "lung being connected with large intestine". For the COVID-19， the diagnosis and treatment plan issued by the National Health Commission clearly proposed the use of intestinal microecological regulator to maintain intestinal microecological balance and prevent secondary bacterial infection. A growing number of studies have shown that lung and intestinal microbial homeostasis plays an important role in pulmonary diseases， termed as specific bacteria and their metabolites are involved in the course of pulmonary diseases. However， the composition of pulmonary and intestinal microorganisms is complex and the mechanism of immune regulation， anti-inflammatory and anti-infection has not been fully declared. In this paper， the research progress of "gut-lung axis"， the lung and gut microbiota in pulmonary diseases combined with the preliminary research of our working group were reviewed and prospected.