Abstract: 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.