【Abstract】〓Objective〓To investigate the value of flow cytometry in the diagnosis of paroxysmal nocturnal hemoglobin (PNH).Method〓61 patients with anemia were selected in October, 2015 March. 2013 in our hospital. According to the condition, the patients were divided into PNH group (24 cases with nocturnal hemoglobin), group AA (24 cases with aplastic anemia), group MDS(4 cases with bone marrow hyperplasia syndrome) and other anemia group (18 cases with other anemia). Flow cytometry was used to detect patients with peripheral blood erythrocytes, granulocytes membrane CD55 and expression of CD59.Results〓The expression of CD55 and CD59 in the red blood cells, the membrane of the PNH group was significantly higher than the other three groups (P<005). There was no significant difference between the AA group and the MDS group (P<005). The expression of CD55 and CD59 in erythrocyte, granulocyte and membrane were all less than 10% in other anemia patients, and the difference was statistically significant (P<005).Conclusion〓Detection of PNH by flow cytometry is highly specific, rapid and accurate, and can effectively help the diagnosis of PNH, which can be used in clinical application.