Bacterial pneumonia accounts for 80% of all types of pathogen pneumonia in adults. Since the advent of the antibiotic era, the prognosis of bacterial pneumonia has improved significantly, but the mortality rate has remained high since the 1960s. At present, some new characteristics of bacterial pneumonia have emerged, including changes in the pathogen spectrum, especially the significant increase in the rate of nosocomial pneumonia g-bacillus. Although Streptococcus pneumoniae still dominates the pathogens of community-acquired pneumonia, the clinical manifestations tend to be atypical. The bacterial resistance rate has increased, and the so-called "refractory" pneumonia is common, especially in children, the elderly and immunosuppressed patients with extremely high mortality rates. Improving the level of etiological diagnosis, rationally using antibiotics, avoiding the emergence of drug-resistant bacteria, and improving supportive treatment are issues that urgently need to be emphasized and resolved in the clinical treatment of pneumonia. According to anatomical classification, pneumonia can be divided into lobar, lobular and interstitial. To facilitate treatment, it is now mostly classified according to the cause, which mainly includes infectious and physical and chemical causes such as radiation, toxic gases, drugs, and allergic reactions such as allergic pneumonia. The vast majority of clinical cases are infectious pneumonia caused by bacteria, viruses, chlamydia, mycoplasma, rickettsia, fungi and parasites, among which bacteria are the most common.