Objective To explore effect of miR-34a on the biological behavior of breast cancer cell MCF-7 by Notch signal pathway. Methods The MCF-7 cells were divided into miR-34a and Control groups. The miR-34a mimics and miR-34a NC were transfected by liposome. The expression of miR-34a in MCF-7 cell was examed by RT-PCR. The cell viability was detected by MTT. The cell apoptosis was examed by Hoechst staining. The cell invasion was detected by transwell method. The expression of Nothch1, Nothc2, Dll1 and Jagged-1 was detected by western blot. Results Compared with Control group, the expression of miR-34a was up-regulated (P<0.01), Cell shrinkage, rounded brighten,the cell viability was decreased (P<0.01), cell apoptotic rate was increased (P<0.01), cell invasion number was reduced (P<0.01), the expression of Notch1, Nothc2, Dll1 and Jagged-1 was down-regulated (P<0.01). Conclusion miR-34a mimics induced MCF-7 cell apoptosis and inhibited cell invasion via inhibition of Notch signal pathway.