In previous research, we found that the Salvia Miltiorrhiza Bunge (SMB), a traditional Chinese medicinal herb, accelerates orthodontic tooth movement. In the present study, to characterize the actions of SMB on bone remodeling, we investigated the effect of SMB on DNA synthesis and alkaline phosphatase activity of murine osteoblast like cell-clone, MC3T3-E1 cells in vitro. Treatment of the cells with SMB for 72 hours caused significant increase in ALPase activity. It was found that SMB increased ALPase activity in a dose-dependent manner, and up to maximum at the concentration of 5.0 mg/ml. At that concentration, ALPase activity was about 135% greater than that of control. SMB at 5.0 mg/ml significantly stimulated ALPase activity of the cells in multilayer on day 8 or calcification stage on day 16, but inhibited it in the sparse stage on day 2 or subconfluency stage on day 4. SMB had no effect on DNA synthesis in any stage of culture. ALPase activity significantly increased at 48 hours and was up to 300% greater than that of control activity at 96 hours. These findings suggest that SMB directly stimulates ALPase activity of MC3T3-E1 cells in multilayer stage or calcification stage without any effect on proliferation. Locally administrated SMB may affect the differentiation of osteoblasts in vivo.