Leukemia M3 (acute promyelocytic leukemia) patients need to wear masks because their immunity is low and they are prone to respiratory infections and other diseases, wearing masks is to prevent respiratory infections, and patients can selectively wear masks after cure. After cure, the bone marrow hematopoietic function is normal, the white blood cells can play normal defense function, the immune function is normal, you can not wear a mask, but in and out of public places, crowded places, it is still recommended to wear a mask to prevent respiratory infections. Acute promyelocytic leukemia (APL) is a special type of acute myeloid leukemia (AML). APL is clinically aggressive and is prone to hemorrhage and embolism during onset and induction therapy, causing death, but it can be cured with aggressive treatment. Drugs include all-trans retinoic acid and arsenic trioxide. After cure of leukemia M3, regular follow-up observation is still needed. Usually, attention should be paid to avoid bacterial and viral infections and prevent relapse. Medications should be administered under the guidance of a physician.