Objective To investigate the effect of fluid shear stress (FSS) on the expression of B lymphoma Mo-MLV insertion region 1 (Bmi-1) in bone mesenchymal stem cells (BMSCs) and possible signal transduction mechanism. Methods BMSCs were isolated from SD rats and FSS at different magnitude (0.5, 1.5, 3.0 Pa) and under different time phase (1, 2, 6, 24 h) were loaded by parallel-plate flow chamber system. The expression of Bmi-1 was measured by real-time RT-PCR at mRNA level and the levels of phosphorylated Akt (p-Akt) and extracellular signalregulated kinase 1/2 (p-ERK1/2) were detected by Western blotting. The signaling inhibitors, wortmannin (PI3K specific inhabitor) and PD98059 (ERK1/2 specific inhabitor), were used to investigate possible mechanical signal transduction pathway. Results Bmi-1mRNA expression increased when BMSCs were exposed to 1.5 Pa FSS for 1 h and reached the peak at 24 h. All FSS with different magnitude could increase Bmi-1 expression, especial at high FSS (3.0 Pa). Meanwhile, FSS resulted in a significant activation of p-Akt and p-ERK1/2 in BMSCs. After treated with wortmannin, the expression of Bmi-1 was inhibited prominently, however, PD98059, the expression of Bmi-1 did not change. Conclusions FSS can activate the expression of Bmi-1, the amount of Bmi-1 expression was closely related to the stimulating time and the magnitude of FSS, and Akt signal molecule plays an important role during the process. These findings provide significant references for studying the mechanical biological mechanisms of stem cell differentiation.