Abstract: AIM: To detect the expression of miR-17-5p between young and aging bone marrow mesenchymal stem cells（BM-MSCs） and to analyze its correlation with cellular senescence.METHODS: BM-MSCs were isolated from bone marrow of Sprague Dawley rats by density gradient centrifugation and cultivated in vitro to the 10th generation.The fourth generation BM-MSCs（P4） and 10th generation BM-MSCs（P10） were stained with β-gal staining.2（-ΔΔct） method was used for quantitative analysis of expression of miR-17-5p between young and aging BM-MSCs by real-time RT-PCR.RESULTS: Morphological changes: P4 to P10 showed cell morphology changes.The shape of P4 cells was highly homogeneous and showed typical swirling growth.P10 cells lost the typical fusiform,increased irregularly in cell volume and were flat and broken in shape.The cell gap increased and showed apoptosis.β-Gal staining results: P10 cells were hypertrophic,blue-stained and positive.P4 cells were not colored after being stained and exhibited negative results.Real-time PCR results: the expression of miR-17-5p in P4 was 6.5 times that of P10（P<0.01）.CONCLUSION: Aging BM-MSCs miR-17-5p expression levels are significantly lower,suggesting that miR-17-5p may be involved in the process of cell aging.