Abstract: Objective To study the effects of kidney-tonifying Chinese herbal drugs on Ca²⁺ intake and mineralization of human osteoblasts in vitro. Methods Human osteoblasts were isolated from the iliac trabecular bone followed by purification and culture at 37 ℃ with 5% CO₂. The cells were identified by cell morphology, calcilum nodule formation and alkaline phosphatase (ALP) activity assay. The third passage of the cultured osteoblasts were treated with 10% scrum from rat fed with the decoction of the kidney-tonifying Chinese herbal drugs of different concentrations for 30 min, 3 d and 28 d, respectively. The cells treated with 10% rat serum without the drugs served as the control. Flow cytometry was used to observe the changes in cell proliferation and intracellular Ca²⁺ concentration, and von Kossa staining employed for quantification of the mineral nodules. Results The osteoblasts obtained were positive for ALP staining and could form calcium nodules in vitro. Flow cytometry showed that the drugs at different concentrations all increased Ca²⁺ influx, as compared with the control cells. The drugs also increased the relative proliferation index of the osteoblasts, and high concentration of the drugs resulted in greater number of the mineral nodules in the osteoblasts (P<0.05). Conclusion The kidney-tonifying Chinese derbal drugs may increase Ca²⁺ influx and stimulate proliferation and differentiation of adult osteoblasts in vitro.