Abstract: OBJECTIVE To study the effect of icariin (ICR) on dexamethasone(DEX)-induced osteogenesis inhibition by activating the estrogen receptor (ER) in MC3T3-E1. METHODS The mature differentiation process of MC3T3-E1 was respectively interfered by adding DEX 10^-5 mol·L^-1, ICR 10^-6 mol·L^-1, estrogen(E2) 10^-8 mol·L^-1 and ICI182780(IN) 10^-5 mol·L^-1, and the real-time RT-PCR, Westen blot, MTT and alizarin red staining were applied for detecting the corresponding change of the indexes. RESULTS ICR could obviously increase the expression of ALP, OPG, OC and Runx2, and significantly reduce the expression of RANKL and Dickkopf in osteoblast as E2. Corresponding protein lever of OPG and RANKL were consistent with the mRNA expression. ALP activity, cell proliferation capacity and Ga²⁺ nodule number increased significantly compared with control group. Meanwhile ICR and E2 were able to effectively revert DEX-induced osteogenesis inhibition, and the regulating effect could be effectively blocked by IN. CONCLUSION ICR can improve osteoblast proliferation differentiation, inhibite osteoclast activation, and effectively relieve the DEX-induced inhibition effect with ER dependent.