Abstract： Objective Toinvestigatetheimmunophenotypiccharacteristicsofacutemyeloidleukemia(AML) patients with NPM1 mutation. Methods The immunophenotype of 237 newly diagnosed AML patients were detected by flow cytometry. Real-time quantitative PCR was employed to detect the NPM1 mutation. The immunophenotype was then compared between the NPM1 mutated and wild type patients. Results The incidence of NPM1 mutation was 19.0 ％ (45/237) in all AML patients.The NPM1 mutated patients had lower expression of CD34,CD117,HLA-DR,CD15 and CD19 than the wild type patients(all P＜0.05).For AML patients with normal karyotype,the incidence of NPM1 mutation was 37.7 ％ (40/106),and the NPM1 mutated patients had lower expression of CD34,HLA-DR,CD15 and CD7 than the wild type patients(all P＜0.05).The NPM1 mutated patients with normal karyotype had lower expression of CD34 HLA-DR and CD7 in M1 subtype(all P ＜ 0.05); lower expression of HLA-DR and higher expression of CD9 in M2 subtype (all P ＜ 0.05) ; and lower expression of CD117 in M5 subtype compared with wild type patients (P ＜0.05). Conclusion The immunophenotypic characteristics of AML patients are changed by NPM1 mutation. The changes of immunophenotype varied in different FAB subtypes.