This paper reported the synthesis of a nano-Hydroxyapatite(HAp)/collagen biocomposite and its biological performances. A thoroughly mixed slurry of type I collagen in supersaturated HAp solution was obtained. HAp was then controlled to precipitate on collagen by adjusting the solution properly. SEM, XRD and TEM analysis reveals that HAp in the composite was nanometer sized and uniformly dispersed oncollagen matrix. In vitro biocompatibility of this new biomaterial was evaluated in terms of its biodegradation and bioactivity. The mice macrophage and osteoblast were used for the study, and the behavior of the cells in contact with the composite was investigated by means of SEM. The observations showed that the composite can be degraded through extracellular resorption process mediated by macrophage, and they can also be well-contact with osteoblast cells, in vitro.