[Objective] To study the effects of total flavonoids from EUCOMMIAE CORTEX on the expression of osteoprotegerin mRNA and protein by osteoblast in vitro cultured from the cranium of newly-born rat.[Method] 10,100 and 200 μg/ml total flavonoids from EUCOMMIAE CORTEX were respectively added into osteoblast isolated from the cranium of SD rats.Then,effects of total flavonoids from EUCOMMIAE CORTEX on the expression of osteoprotegerin mRNA and protein were respectively detected by Realtime-PCR and immunofluorescence technique.[Result] Compared with control group,total flavonoids from EUCOMMIAE CORTEX could obviously promote the expression of osteoprotegerin mRNA and protein by osteoblast.[Conclusion] Total flavonoids from EUCOMMIAE CORTEX could directly promote the expression of osteoprotegerin by osteoblast at the RNA and protein level. [Objective] To study the effects of total flavonoids from EUCOMMIAE CORTEX on the expression of osteoprotegerin mRNA and protein by osteoblast in vitro cultured from the cranium of newly born baker. [Method] 10,100 and 200 μg / ml total flavonoids from EUCOMMIAE CORTEX were respectively added into osteoblast isolated from the cranium of SD rats. Chen, effects of total flavonoids from EUCOMMIAE CORTEX on the expression of osteoprotegerin mRNA and protein were respectively detected by Realtime-PCR and immunofluorescence technique. [Result] Compared with control group, total flavonoids from EUCOMMIAE CORTEX could substantially promote the expression of osteoprotegerin mRNA and protein by osteoblast. [Conclusion] Total flavonoids from EUCOMMIAE CORTEX could directly promote the expression of osteoprotegerin by osteoblast at the RNA and protein level.