Abstract: Objective：To investigate the effect of let-7c on the proliferation and odonto/osteogenesis differentiation of rat bone marrow mesenchymal stem cells in vitro. Methods：Rno-let-7c over / low lentiviral vector were constructed and used to transfect rat BMMSCs in vitro, then the optimal transfection titer was screened. The of green fluorescent protein was observed by inverted fluorescence microscope. Real-time quantitative RT-PCR was used to verify the efficiency of rno-let-7c transfection. The effect of rno-let-7c on rBMMSCs proliferation and apoptosis was detected by CCK-8 and Flow Cytometry. The of insulin-like growth factor 1 receptor (IGF-1R) and odonto/osteogenic markers (RUNX2/OSX/OCN/DMP1) were detected by western blot. Results： The optimal condition of lentiviral vector to transfect rBMMSCs was MOI=3. Rno-let-7c over/low BMMSCs model was constructed successfully. Rno-let-7c over/low had no significant effect on proliferation and apoptosis of rat BMMSCs (P>0.05). Compared with the negative transfection group, the of IGF-1R and odonto/osteogenic markers was down-regulated in over group, while the of IGF-1R and odonto/osteogenic markers was up-regulated in low group (P>0.05). Conclusions：Let-7c had no obvious effect on the proliferation and apoptosis of rat BMMSCs. Let-7c can inhibit the odonto/osteogenic differentiation of rat BMMSCs.