Abstract: Objective: To study the effects of Citrated Calcium Sulphate（CCaS） on osteoblasts function and explore the possibility of this biomaterial as bone graft substitutes. Methods: Using the method of in vitro cell culcure,the influences of CCaS on the osteoblasts functions,such as cell proliferation,ALP activity,osteocalcin production,were detected. Results: Osteoblasts cultured in DMEM containing 100% concentration CCaS solutions growed slightly slower,but their relatively growth rates（RGR） were superior to 90%.They had the same AgNOR number as in control group,and excreted much more ALP and osteocalcin compared to in control group. Conclusion: CCaS has no toxtic effects on osteoblasts and stimulates the proliferation and differentiation of osteoblasts.