Objective To investigate the expression and clinical significance of miR-125b in patients before and after treatment of acute myeloid leukemia (AML) with different types.Methods The levels of miR-125b were measured by using real-time fluorescence quantification PCR (qRT-PCR) in 65 AML patients (all AML samples from the Sun Yat-Sen Memorial Hospital of Sun Yat-Sen University,and the control samples isolated from cord blood which were obtained after normal full-term delivery of babies) before and after treatment,and then the relationship between the levels of miR-125b and patients＇ sex,age,peripheral blood cells,type clinically,relapse and therapeutic effect were analyzed.Results Of newly diagnosed AML patients and the control samples,miR-125b positive rate was 100％.The miR-125b expression levels in the control group was 1.50,and its expression in AML was 11.06,and the difference was significant (P =0.036 6).In complete remission (CR) group of acute promyelocytic leukemia (M3),the expression of miR-125b after induction therapy was significantly reduced,and CR rate of miR-125b decreased group was 91.3％,while that of the increased group was 50.0％,and the difference was significant (P =0.042 6).The miR-125 b expression level was decreased from 29.7 ± 4.9 to 19.2 ± 6.0 after chemotherapy,and the difference was significant (P ＜ 0.036 6).In non-M3 AML,CR rate of miR-125 b decreased group was 86.7 ％,while that of the increase group was 42.1％,and the difference was significant (P =0.021 5).There was no correlation between miR-125b expression and patients＇ gender,age and peripheral blood cells.Conclusions The differences in expression of miR-125b is very important in disease occurrence and progress.Using qRT-PCR to dynamically detect the expression of miR-125b dynamically in AML patients before and after therapy may predict outcome more precisely and has the potentials as an effective biomarker in determining prognosis,monitoring the risk of recurrence,and guiding the treatment.