Abstract: Nano-sized hydroxyapatite powder was synthesized by chemical precipitation method.Influences of factors,such as concentration and proportion of reactants,pH value of the system,dispersant dosage,reaction temperature,and time,on average particle size of the product were investigated.Process parameter scopes were groped through single factor experiment.Then primary parameters were selected to do orthogonal tests.Optimum process conditions were obtained.Particle size and crystallinity degree of the product were characterized by particle size analyzer,TEM,FT-IR spectroscopy,X-ray diffraction(XRD) and so on.Results showed that hydroxyapatite powder synthesized under the optimum conditions could achieve nano-grade,and had uniform size distribution,high purity and better crystallinity.