Abstract: Objective: To investigate the expression level of Wilms'tumor 1(WT1) gene in bone marrow of acute leukemia(AL) patients.Methods:The copy numbers of WT1 and reference gene in BM of 100 patients with AL were measured by real-time quantitative polymerase chain reaction (RQ-PCR).The gene level was determined by the ratio of the copy numbers of WT1 and reference gene.Results:The expression levels of WT1 in the newly diagnosed and relapsed AL patients were significantly higher than that in the complete remission(CR) AL patients(P0.01).In newly diagnosed AL patients,the WT1 expression difference in different subtype of AL was statistical significance(P0.01),the WT1 expression was the lowest in acute lymphocytic leukemia and the highest in acute promyelocytic leukemia.Three patients were followed up,the WT1 gene expression was low in the remission period,and increased after relapse.Conclusions:WT1 expression level in AL patients can be a marker for detecting minimal residual disease and evaluating therapy efficacy.