To investigate the clinical, cellular morphology, immunophenotype, and cytogenetic characteristics of acute myeloid leukemia (AML) which are very similar to the morphological characteristics of prolymphocytic leukemia (PLL), the morphological features of bone marrow cells from patient were observed by light microscope, the immunophenotypes were detected by flow cytometry, the karyotypes were analyzed by conventional cytogenetic method, the hybridization signals were determined by fluorescence in situ hybridization. The results indicated that the clinical features were in accordance with acute leukemia and the immunophenotyping results showed malignant cells originated from myeloid lineage, while the cytomorphology analysis showed that the blastic cells were more like the lymphoid lineage. Trisomy 8 was found in the patient by cytogenetic study, the patient did not show good response to chemotherapy. In conclusion, acute leukemia has high heterogenicity, which could be defined as AML, but more like lymphocytic origination by morphological study. Immunophenotyping analysis could contribute to the final diagnosis of malignant cells.