In order to investigate the expression of CD56 on acute leukemia cells and its clinical significance, samples from 70 patients with acute leukemia were analyzed with multicolor flow cytometry to determine the CD56 and other leukocyte differentiation antigens. The results showed that 16 of 70 cases (22.86%) were identified to express CD56, of which 1/35 (2.86%) patient with acute lymphocytic leukemia (ALL) and 15/31 (48.39%) with acute myelocytic leukemia (AML) were CD56 positive. The positive rate of CD56 in AML was significantly higher than that in ALL (P < 0.01). The expression of CD56 varied in AML subtypes. The positive rate (11/15) of CD56 in AML-M(0), -M(1) and -M(2) was significantly higher than that in AML-M(3), -M(4) and -M(5) (4/16) (P = 0.013). 13 of 15 AML with CD56 expression were also positive for HLA-DR (41.94%), and a significant positive correlation was found between the expression of CD56 and HLA-DR (r = 0.439, P = 0.014). It was concluded that CD56 mainly expressed in AML cells. The analysis of CD56 expression on acute leukemia is of great value in the diagnosis, prognosis prediction and monitoring of minimal residual disease in AML patients.