Hydroxyapatite　(HA)　+　yttria　stabilized　zirconia　(YSZ)　bio-composite　coatings　deposited　onto　Ti-6Al-4V　substrate　through　a　micro-plasma　spray　(MPS)　technique　were　immersed　in　simulated　body　fluid　(SBF)　to　investigate　their　behavior　in　vitro.　The　formation　of　apatite　on　their　surface　was　investigated　to　evaluate　the　bioactivity　of　the　coatings.　Surface　morphologies　and　structure　in　the　coatings　were　analyzed　by　scanning　electron　microscopy　(SEM),　X-ray　diffractometer　(XRD).　Results　showed　that　composite　coatings　consist　of　primitive　cubic　phase　ZrO2,　a　quantity　of　α-Ca3(PO4)2　can　be　found　because　of　the　decomposition　of　HA　at　high　temperature　and　the　rapid　cooling　rate　during　MPS.　Composite　coatings　contain　some　unmelted　small　ZrO2　particles,　though　the　HA　melted　well.　Apatite　can　be　formed　on　the　coating　soaked　in　SBF　solution,　which　indicated　that　zirconia　reinforced　hydroxyapatite　composite　coatings　possessed　excellent　bioactivity.