Objective To investigate the clinical characteristics of diffuse alveolar hemorrhage. Methods 12 patients with diffuse alveolar hemorrhage hospitalized in Guangzhou NO.1 Hospital were included in the research, whose clinical characteristics were analyzed. Results 7 cases of the 12 diffuse alveolar hemorrhage cases were male and 5 cases were female. 8 cases were caused by ANCA associated vasculitis , 1 cases by connective tissue disease, 1 cases by poisoning, and 2 cases of unknown etiology (medication could be considered). The clinical manifestations were fever (91.67%), hemoptysis (100%), anemia (100%), and dyspnea (3.33%). Conclusion Diffuse alveolar hemorrhage is a life-threatening clinical syndrome. It can be caused by many causes. It should be considered if there is the presence of hemoptysis, dyspnea, anemia, etc. Timely examination and early intervention can effectively improve the prognosis of the disease.