Objective: To build mouse osteoblast MC3T3-E1 and mouse osteoclast RAW264.7 co-culture system and to study the effect of icariin on the activity of osteoblasts and osteoclasts in the co-culture system. Methods: In vitro acquisition and cultivation of mouse osteoblasts MC3T3-E1 and mouse RAW264.7 cells were conducted. Osteoblast and osteoclast activities of cells were detected by CCK-8 staining experiment, alizarin red staining and tartaric-resistant acid phosphatase (TRAP) staining. We used different concentrations of icariin to interfere in osteoblast-osteoclast co-culture system. The effects of icariin on various genes were detected by PCR and Western blot methods The correction between the expression of PPAR gamma and BMD was analyzed in patients with osteoporosis. Results: Mouse osteoblast-osteoclast co-culture system was built, and the osteogenic differentiation effect was enhanced. Icariin can improve the MC3T3-E1 osteogenic differentiation activity, enhance the expression of OPG and RANKL gene protein, reduce the NF-(k)b gene and protein expression, increase of ALP, TGF-b1 and RANKL gene expression level and reduce RANK gene expression. Icariin can act on MC3T3-E1 cells-RAW264.7 cells co-culture system, and promote the osteogenic activity of MC3T3-E1 cells, inhibit the osteoclast activity of RAW264.7 cells and reduce the level of BMSCs adipogenic differentiation. The expression level of PPAR-g gene was negatively correlated with the level of BMD. Conclusions: Mouse MC3T3-E1 cells and mouse RAW264.7 cells could be co-cultured in vitro, and icariin could improve the osteogenic activity of MC3T3 cells-RAW264.7 cells and decrease the osteoclast activity. Icariin could inhibit adipogenic differentiation of BMSCs in the osteoblast-osteoclast co-culture, promoting osteogenic differentiation and inhibiting osteoclast differentiation. (C) 2017 Elsevier Masson SAS. All rights reserved.