Aplastic anemia (AA) is a disease in which the bone marrow hematopoietic stem cells and the bone marrow microenvironment are severely damaged by physical, chemical, biological or unknown factors, resulting in a decrease or failure of the bone marrow hematopoietic function. It is a group of syndromes with pancytopenia as the main manifestation. According to a survey in 21 provinces (cities) and autonomous regions in China, the annual incidence rate is 0.74/100,000 population, which is significantly lower than the incidence rate of leukemia; the incidence rate of chronic aplastic anemia is 0.60/100,000 population, and the incidence rate of acute aplastic anemia is 0.14/100,000 population; it can occur in all age groups, but it is more common in young and middle-aged people; the incidence rate in men is slightly higher than that in women.