Abstract: A new kind of injectable composite of nano hydroxyapatite/aspartic acid-glutamic acid copolymer/calcium sulfate(nano HA/PAG/CS) was prepared by using polymerization in situ. The composition, structure, surface morphology and mechanical strength of the composite were characterized by FTIR, XRD and SEM etc, and its degradability was investigated in simulated body liquid(SBF). The results show that the interaction appear between the inorganic and organic phase of the composite. The composite exhibits good compressive strength and degrads totally after soaking in SBF for 7 weeks with surface degradation methods. In the degradation process, the pH of SBF solution changes from 6.4 to 7.4. The composite has good bioactivity because the apatite can be formed on its surfaces after soaking into SBF, which is very useful for the formation of interface combination between implant and tissue.