M3 is acute promyelocytic leukemia, which is a type of acute myeloid leukemia and is currently the best treated type of leukemia. Due to the application of retinoic acid and arsenious acid, the cure rate of M3 is over 90%, and there are still a few patients who will relapse. The common methods of how to prevent the relapse of M3 are: First, regular bone marrow aspiration examination to check the tiny residual lesions, if the tiny residual lesions are positive, only timely administration of arsenious acid, retinoic acid and chemotherapy, which can effectively reduce the relapse. Second, M3 patients should usually pay attention to rest and avoid infection, especially avoid viral infection, which can reduce the possibility of recurrence to a certain extent. Third, avoid some drugs that have obvious side effects on the hematological system, such as etidiumorphine, etc., because these drugs may cause M3 to relapse.