Objective To investigate the K562 cells biological function and related molecular changes in PTEN-PI3K/AKT signaling pathway of leukemia K562 cells by inhibiting the miRNA-21 expression to explore its pathogenesis of leukemia.Methods The chemical synthetic miRNA-21 inhibitor was transfered into K562 cells by electrotransfection.RT-PCR was used to detect the miRNA-21 expression changes.Cell proliferation and apoptosis were determined by using MTT and flow cytometry.Western-blot were used to detect the protein expression changes of PTEN,PI3K and p-AKT respectively.Results The relative expression of miRNA-21 in experimental group was (8.070±5.138)％ at 24 hours,which was lower than control groups (P＜0.05).The apoptotic rate of (13.370±0.250)％ at 24 hours in experimental group was obviously higher than control groups.The cellular proliferation were significantly different at 24 hours.The proliferation inhibition rate was (8.1±0.9)％ at 24 hours,which was up to (43.1±2.1)％ at 60 hours,but the control groups showed no difference.K562 cell proliferation significantly decreased,while cell apoptosis markedly increased by inhibiting miRNA-21 expression (P＜0.01).Western-blot analysis revealed up-regulation of PTEN and down-regulation of PI3K and p-AKT protein expressions after successfully suppressed miRNA-21 expression (P＜0.01).Conclusion Inhibiting miRNA-21 expression in K562 cell could suppress the PI3K/AKT pathway by up-regulation of PTEN expression and promote cell antiproliferative and pro-apoptosis effects.