Abstract: Objective To summarize the experience of diagnosis and treatment on diffuse alveolar hemorrhage (DAH) in patients with hematopoietic system diseases. Methods Clinical data about 21 cases with diffuse alveolar hemorrhage secondary to hematopoietic system diseases from October 2004 to October 2014 in department of hematology, Navy General Hospital, were retrospectively analyzed. Results Of the 21 cases, 14 cases were acute non-lymphoblastic leukemia, 5 cases were acute lymphoblastic leukemia, and 2 cases were severe aplastic anemia. The onset time of this disease was during or after leukemia chemotherapy in 15 cases, preconditioning or post-transplantation in 3 cases, and during palliative treatment in 4 cases. Clinical presentations included dyspnea (100%), hypoxaemia (100%), fever (90.5%), bloody-sputum (71.4%), and hemoptysis (19.1%). Chest image:15 cases showed diffuse parenchymal exudates, 6 cases showed ground-glass interstitial change and 7 cases showed a small amount of bilateral pleural effusion. The mortality rate was 76.2% (16/21). Conclusion DAH secondary to hematopoietic system diseases shows high mortality. Dyspnea, fever, bloody sputum, hemoptysis, and diffuse lung infiltration provide clues for diagnosis. Early identification and treatment may improve outcomes.