Hydroxyapatite　(HA)　is　one　of　the　most　important　bioceramic　materials　used　in　medical　implants.　The　structure　of　HA　coatings　is　closely　related　to　their　manufacturing　process.　In　the　present　study,　HA　coatings　were　deposited　on　Ti-6Al-4V　substrate　by　micro-plasma　spraying.　Results　show　that　three　distinct　HA　coatings　could　be　obtained　by　changing　the　spraying　power　from　0.5　to　1.0　kW　and　spraying　stand-off　distance　from　60　to　110　mm:　(1)　high　crystallinity　(93.3%)　coatings　with　porous　structure,　(2)　high　crystallinity　coatings　(86%)　with　columnar　structure,　(3)　higher　amorphous　calcium　phosphate　(ACP,　50%)　coatings　with　dense　structure.　The　in-flight　particles　melting　state　and　splat　topography　was　analyzed　to　better　understand　the　formation　mechanism　of　three　distinct　HA　coatings.　Results　show　that　HA　coatings　sprayed　at　low　spraying　power　and　short　stand-off　distance　exhibit　high　crystallinity　and　porosity　is　attributed　to　the　presence　of　partially　melted　particles.　High　crystallinity　HA　coatings　with　(002)　crystallographic　texture　could　be　deposited　due　to　the　complete　melting　of　the　in-flight　particles　and　low　cooling　rate　of　the　disk　shape　splats　under　higher　spraying　power　and　shorter　SOD.　However,　splashed　shape　splats　with　relative　high　cooling　can　be　provided　by　increasing　SOD,　which　leads　to　the　formation　of　ACP.