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　crys-tallinity　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.