Objective To investigate the differential expression of microRNA-155 in new diagnosed pediatric acute myeloid leukemia (AML) and its clinical significances. Methods 19 AML children and 20 non-leukemia controlled children were included. Real-time quantitative PCR (TaqMan）was applied to validate the expression of microRNA-155 in bone marrow samples. Results The expressions of microRNA-155 in AML children were significantly higher than those in controls (p=0.001). The levels of microRNA-155 had no significant differences in Karyotype groups, response to treatment groups and risk groups (p>0.05). The microRNA-155 levels in AML childen were increased comparing with controls, but there were no distinctions in clinical groups associated with the outcome of disease. Conclusion The microRNA-155 may be used as one of biomarkers in the early diagnosis of childhood AML in the near future.