Pulmonary infectious disease is one of the main type of the respiratory system disease. Ventilator associated pneumonia(VAP) is a major cause for prolonged hospitalization days and higher mortality in ICU. However, Along with changes in personal and public health environment, as well as the increase of drug-resistant bacteria and the expansion of the susceptible population, a large transition has occurred in the epidemiology of pulmonary infectious disease in recent years. This alteration has undoubtedly made clinical work in ICU more difficult, whereas brings up hints on diagnosis and treatment for pulmonary infectious diseases and also suggests our limitations in prevention, diagnosis and anti-infection treatment.