Pyothorax is a purulent infection in which purulent exudate accumulates in the chest cavity. It is mainly divided into different types in terms of lesion scope, different pathogens and pathological development process. (1) According to the scope of lesion, it is divided into total abscess thorax and limited abscess thorax. Total abscess thorax refers to pus occupying the whole pleural cavity, and confined abscess thorax refers to pus accumulating between the lung and chest wall or transverse or longitudinal septum, or between the lung lobes and lung lobes, also called wrapped abscess thorax. (2) According to the different pathogens, it can be divided into non-specific pustulothorax and specific pustulothorax. General bacterial infection is non-specific pustulothorax, while tuberculosis or amoebic protozoal infection is specific pustulothorax, which can also be directly called tuberculous pustulothorax or amoebic pustulothorax. The pus caused by mixed strains of infection including anaerobic bacteria is dark gray, thick and foul-smelling, which is called corrosive pustulothorax. (3) Sepsis can be divided into acute and first chronic according to the pathological development of all. The course of the disease within 4-6 weeks is acute pustulothorax, and the early stage is dominated by a large amount of exudate, which is called exudative period. In this period, if the exudate is removed and the infection is controlled, the abscess chest can be cured and the lung can be well reopened. If the exudate is not cleared and a large amount of fibrin is deposited, the fibrin membrane is formed and enters the fibrous septic phase, and then the fibrin membrane is mechanized to form a fibrous plate and calcified, the septic chest enters the mechanized phase, which is the chronic septic chest. If the treatment of acute abscess chest is not timely, inappropriate or incomplete, it will turn into chronic abscess chest.