Abstract: Objective To investigate the effect of PTEN/PI3K/Akt signal pathway on cell proliferation, apoptosis and its possible apoptosis-related molecular mechanism on human chronic myeloid leukemia (CML) cell line K562 cells. Methods The recombinant adenovirus containing green fluorescent protein (GFP) and PTEN（Ad-PTEN-GFP）or empty vector （Ad-GFP）was transfected into K562 cells. The growth of K562 cells was observed by MTT assay; the apoptosis rate and proliferation index (PI) were assessed by flow cytometry (FCM). We also detected apoptosis by morphology, DNA and transmission electron microscope technique; PTEN together with anti-apoptosis gene Bcl-2, Bcl-xL mRNA and apoptosis gene Bax mRNA levels were detected by real-time fluorescent relative-quantification reverse transcriptional PCR(FQ-PCR). PTEN and p-Akt protein levels were detected by western blotting. Results Compared with Ad-GFP growth, the growth of K562 cells transfected by Ad-PTEN-GFP was suppressed markedly, proliferation index (PI) was down regulated, apoptosis rate rised and p-Akt expression levels decreased but not total Akt; Bcl-2, Bcl-_xL mRNA levels descend and Bax mRNA level increased after transfected with wild type PTEN. Conclusion Over expression PTEN gene might inhibit K562 cells proliferation and promote cell apoptosis via down regulation PI3K/Akt pathway.