Abstract: Objective To investigate the expression and significance of cyclooxygenase-2 （COX-2） and evaluate its potential impact on the prognosis in acute myeloid leukemia（AML）. Methods The mRNA level of COX-2 in AML was detected by Real time-PCR. The relevance between COX-2 expression and clinical features of AML was assayed. The relation between COX-2 expression and overall survival（OS）was analyzed by Kaplan-Meier method. Results The average relative quantity of COX-2 mRNA in 38 AML patients was 4.77±2.21，and among them，20 patients were of high expression（8.33±1.96），and 18 were of low expression（1.89±1.04）. The expression of COX-2 was correlated with initial leukocyte count and the initial response to therapy，but not with gender and age. Furthermore，the median OS of patients with high expression of COX-2 was 16.2 months，shorter than 25.6 months of low expression（P=0.041）. Conclusion The expression of COX-2 in AML was associated with prognosis， and high expression of COX-2 may be a poor prognostic factor in AML.