Objective To investigate the role of Rho in SiO2 induced α-SMA expression in human bronchial epithelial cells (HBECs). Methods HBECs were cultured and stimulated with SiO2. Immunocytochemistry and Western blot were used to detect the expression of α-SMA. The activity of Rho was determined by GST pull down assay. In the prevention experiment,SiO2-stimulated HBECs were incubated with Rho inhibitor Y27632,and the expression of α-SMA was examined by Western blot. Results With SiO2 (0-300 μg/mL) treatment,the expression of α-SMA increased gradually,and 200 μg/mL of SiO2 led to the highest expression of α-SMA which was (5.09±1.98) times of the expression of α-SMA in the control group(P＜0.01). HBECs treated with SiO2 (200 μg/mL) for indicated time (1,2,6,12,and 24 h)showed an obvious increase of Rho activity(P＜0.01). Y27632 inhibited SiO2-induced α-SMA expression significantly,and the inhibition rate of 20 and 30 μmol/L Y27632 was 68% and 75%,respectively (P＜0.01).Conclusion Rho signaling pathway may mediate SiO2 induced α-SMA expression in HBECs.