Objective: Study the immunophenotype of acute leukemias using flow cytometry method. Subject and method: the authors retrospectively collected data of immunophenotyping from 43 acute leukemia patients at the Hematology Department in No.108 Military Central Hospital from October 2013 to February 2015. Patients were diagnosed and classified based on peripheral blood and bone marrow examination for morphology, cytochemistry and immunophenotypic studies. Result: All patients were adults with male/female ratio of 3.3/1. Out of total 43 cases of acute leukemia diagnosed by flow cytometry, there were 36 cases (83.7 percent) of acute myelogenous leukemia, 6 cases (14 percent) of acute lymphoblastic leukemia and one case (2.3 percent) of bi-phenotypic acute leukemia when using morphology and cytochemistry alone, there were still 4 cases which could not be classified clearly that they were acute myelogenous leukemia or acute lymphoblastic leukemia. Out of that 4 cases, 3 cases were acute myelogenous leukemia and 1 case was bi-phenotype when diagnosed by immunophentyping. Conclusion: Flow cytometric immuno-phenotyping is power tool for classification of acute leukemias in to acute myelogenous leukemia or acute lymphoblastic leukemia. Particularly, it can correct identification of T and B cell lineage of acute lymphoblastic leukemia and diagnosis of biphenotypic acute leukemia.