Abstract: Objective To evaluate the effect of microRNA-21 on migration of Flk1+ mesenchymal stem cells (MSCs). Methods Flk1+MSCs were transfected with microRNA-21 inhibitor using Lipofectamin2000 and their migratory activity was evaluated by transwell. Taqman real-time PCR was applied to detect expression of microRNA. Results Compared to control group, the expression of microRNA-21 was significantly reduced in the inhibitor-transfected group. Moreover, the number of cells migrated through transwell in the inhibitor-transfected group was 77.5%, 71.3% and 69.8% of that in the control group at 12、16 and 20h , respectively. Conclusion microRNA-21 can regulate the migratory capacity of Flk1+MSCs.