How many years it takes to pass the danger period after chemotherapy for leukemia varies from person to person, and is related to the patient’s age, physical fitness, the type of disease, the dose of chemotherapy, and the sensitivity of the disease to chemotherapy, etc. Generally, it takes 2~4 weeks to pass the danger period and enter the bone marrow recovery period. After chemotherapy for leukemia patients, chemotherapeutic drugs can cause the bone marrow to show transient hematopoietic cell growth inhibition, leading to a decline in platelets, peripheral blood red blood cells, granulocytes, resulting in patients with dangerous symptoms such as anemia, fatigue, infection and bleeding. The earlier the above dangerous symptoms appear, the slower the recovery will be. In addition, different chemotherapeutic drugs inhibit the bone marrow for different periods of time, and therefore, the length of the danger period varies. Generally, the risk period begins after chemotherapy is stopped, and lasts for 2 to 4 weeks. After anti-infection, hemostasis, promotion of hematopoiesis and supportive treatment, some patients can pass the risk period and enter the bone marrow recovery period. The specific time to pass the dangerous period is related to the patient’s age, physical fitness, the type of disease, the dose of chemotherapy, the sensitivity of the disease to chemotherapy, etc. Regular follow-up and review are recommended. For the same disease, patients with different physical conditions and different stages of the disease have different treatments, and should be treated in a standardized manner under the guidance of a doctor.