The first course of m3 leukemia is the danger period. m3 leukemia, or acute promyelocytic leukemia, is an acute myeloid leukemia that accounts for 10-15% of all acute myeloid leukemias and manifests as promyelocytosis. Symptoms are anemia, infection and fever. According to the current treatment in China, 3 stages of treatment are generally required. The first stage is induction therapy, the second stage is consolidation therapy, and the third stage is maintenance therapy. Drugs include all-trans retinoic acid, arsenic trioxide, and cytarabine. Bleeding, embolism, and differentiation syndrome are prone to occur during induction therapy causing patient death. Therefore, the first course of treatment is the dangerous period. In the treatment, it is necessary to strictly follow the doctor’s instructions and communicate with the doctor in case of abnormalities.