The study was aimed to investigate the immunological characteristics and prognosis of acute myeloid leukemia (AML) M(1) and to find the main points in immunology to differentiate AML M(1) from M(2), and M(1) from ALL (proB, preB, T). Immunophenotyping was performed in 41 AML M(1) patients by three-color flow cytometry analysis using CD45/SSC gating, meanwhile the cytogenetic analysis was performed in 17 patients. 51 newly diagnosed AML M(2) patients and 58 newly diagnosed ALL patients were used as control at the same time. The results showed that the positive rate of CD33 in M(1) was 100%, which was high in sensitivity, but low in specificity; the positive rate of CD11b, CD15, MPO, CD117 in M(1) were significantly lower than that in M(2) (p < 0.05); the positive rate of T-lineage antigen in Ly + AML M(1) was higher than that in M(2) (p < 0.05); compared with ALL ProB, M(1) had high expression of HLA-DR, simultaneously myeloid antigen CD13, CD15, CD33, CD117, MPO and T-lineage antigen CD4, CD7 were all highly expressed (p < 0.05); compared with ALL PreB, M(1) had high expression of HLA-DR, CD34, meanwhile myeloid antigen CD13, CD15, CD33, CD117, MPO and T-lineage antigen CD4, CD5 were all highly expressed (p < 0.05); as compared with T-ALL, the early-phase antigen HLA-DR, CD34, myeloid antigen CD13, CD15, CD33, CD117, MPO of M(1) were all significantly highly expressed (p < 0.05). In M(1), the complete remission (CR) rate in patients with CD7 positive had no statistical difference from that in patients with CD7 negative (p > 0.05); the CR rate of patients with CD34 positive had no statistical difference from that of patients with CD34 negative (p > 0.05); CR rate in M(1) was lower than that in M(2) (p < 0.05), time to reach CR was longer, the incidence of hyperleukocytic acute leukemia was higher (p < 0.05), CR rate in hyperleukocytic acute leukemia was lower (p < 0.05). It is concluded that the myeloid antigen CD33, CD13 in M(1) are highly expressed, early-phase antigen HLA-DR in M(1) is also highly expressed, but the myeloid antigen CD11b, CD15, MPO, CD117 in M(1) are lowly expressed, T-lineage antigen CD4, CD7 in M(1) are highly expressed in the meantime. There is no definite characteristic marker in immunology to differentiate M(1) from M(2), but as the positive rate of CD11b, CD15, MPO, CD117 in M(1) are significantly lower than that of M(2), CD11b, CD15, MPO, CD117 can be used as reference indicators to differentiate M(1) from M(2). AML M(1), ALL ProB, ALL PreB and T-ALL, which are difficult to differentiate in morphology can be well seperated through the analysis of immunological phenotype. CD117 is mainly expressed in AML, which is useful for the differentiation diagnosis between AML and ALL. The prognosis of M(1) is worse than that of M(2).