Abstract: Hydroxyapatite(HA) coatings on Ti6Al4V substrate were deposited by atmospheric plasma spraying(APS) process.The microstructure of HA coatings was studied by optical and scanning electron microscope(SEM),and X-ray diffractometer(XRD) was applied to investigating the phase composition and crystallinity of the coatings.Relationship of crystallinity and plasma parameters were investigated.Experimental results indicate that HA partially decomposes into impurities such as TCP,TTCP and CaO,et al,and amorphous phase formes because of fast cooling rate of the molten particle.The decrease of current,spraying distance and assistant gas flow could increase the crystallinity with a decrease of the impurities.Cross-sectional morphology of coating 1^#(crystallinity=34.8%)exhibits a typical lamellar structure with seldom unmolten particles while coating 2^#(crystallinity=43.9%)and 3^#(crystallinity=50.6%) are in reverse.