Hydroxyapatite whiskers are used as reinforcement for biomaterials because of their needlelike morphology and strong strength of single crystal. HAP nanoparitcles are used in drug delivery system, protein separation and anticancer drug besides their implant applications. Many new properties arise from nanoeffects while nanoeffects come from specialty of nanostructure. The Ca(NO3)2·4H2O and (NH4)2HPO4 were used as starting reagents for preparation of HAP whiskers and nanoparticles. The whiskers are 100-200μm long while nanoparticles are 30-80nm in size. XRD is applied to characterize the lattice parameter difference of whisker and nanoparticle. Compared with those of HAP whiskers, the a-axis and b-axis of HAP nanocrystals are shortened while the c-axis is elongated. That makes nanoparticles capable of their non-needle-like morphology, higher reaction activity and special bioeffects