The biological HA in the body differs from that of pure HA in stoichiometry, composition, physical properties and mechanical properties, because this HA is particularly prone to ion substitution. As a cation that can substitute for calcium in the structure of hydroxyapatite, strontium provokes an increasing interest because of its beneficial effect on bone formation, and prevention of bone resorption. Here, strontium-substituted HA powders were prepared by the hydrothermal method at 180℃ for 8 h using Ca(NO3)2·4H2O, (NH4)2HPO4 and Sr(NO3)2 as reagents. X-ray diffraction, Fourier transform infrared spectroscope, transmission electron microscope, energy dis- persive X-ray, and thermogravimetric-differential thermal analysis were employed to investigate the crystalline phase, chemical composition, morphology, and thermal stability of the Sr-HA. And the cytotoxicity of Sr-HA was analyzed through MTT assay. The results show that Sr is incorporated into the HA crystal structure and the crystal grain size of the Sr-HA decreases as the Sr content (under 50wt%) is increased. Moreover, the HA thermal stability decreases. However, there's no apparent difference between the pure hydroxyapatite and all of the Sr-HA groups in cytotoxicity, which may have good biocompatibility.