Objective To analyze the mRNA expression level of lymphoid enhance factor 1 (LEF-1), and to investigate its clinical significance in bone marrow mononuclear cells of patients with chronic myeloid leukemia chronic-phase (CML-CP) after initial diagnosis and chemotherapy, and to analyze its clinical significance. Methods The real-time fluorescence quantitative polymerase chain reaction was used to measure the expression level of LEF-1 gene in 38 CML-CP patients after initial diagnosis and chemotherapy and 20 persons without blood system diseases and neoplastic diseases as normal control. The difference of LEF-1 expression level between the patients and healthy control was compared, and the effect of imatinib on the main molecular response (MMR) was analyzed. Results The expression of LEF-1 mRNA in 38 newly diagnosed patients [0.00214 (0.00020 - 0.02120)] was significantly higher than that in normal controls [0.00101 (0.00009 - 0.00233)] (U= 163.0, P< 0.01). The expression of LEF-1 mRNA in MMR group [0.00107 (0.00010 - 0.00519)] was significantly lower than that in non-MMR group [0.01015 (0.00091 -0.03615)] (U= 25.0, P< 0.01). There was no significant difference in LEF-1 mRNA expression between the normal control group and the MMR group after imatinib treatment (U= 201.0, P> 0.05). The level of LEF-1 mRNA expression of non-MMR group was also higher than that of the normal control group (U= 14.0, P<0.01). The rate of acquiring MMR was significantly higher in high LEF-1 mRNA expression group [84.2 %(16/19)] than that in low expression group [47.4%(9/19)] (χ2=4.209, P<0.01). The time of acquiring MMR was significantly shorter in the high LEF-1 mRNA expression group [(10.0 ± 4.5) months] than that in the low expression group [(14.6 ± 3.8) months] (t= 2.705, P< 0.01). Conclusions LEF-1 may be involved in the occurrence and development of CML, and reflects the tumor burden. It may be one of the indicators to predict the efficacy of imatinib.