Effect of the addition of trace HA particles into Mg-2Zn-0.5Sr on microstructure,mechanical properties,and bio-corrosion behavior was investigated in comparison with pure Mg.Microstructures of the Mg-2Zn-0.5Sr-xHA composites (x=0,0.1 and 0.3 wt%) were characterized by optical microscopy (OM),scanning electron microscopy (SEM) equipped with energy dispersion spectroscopy (EDS) and X-ray diffraction (XRD).Results of tensile tests at room temperature show that yield strength (YS) of Mg 2Zn-0.5Sr/HA composites increases significantly,but the ultimate tensile strength (UTS) and elongation decrease with the addition of HA particles from 0 up to 0.3 wt%.Bio-corrosion behavior was investigated by immersion tests and electrochemical tests.Electrochemical tests show that corrosion potential (Ecorr) of Mg-2Zn-0.5Sr/HA composites significantly shifts toward nobler direction from-1724 to-1660 mVSCE and the corrosion current density decreases from 479.8 to 280.8 μA cm-2 with the addition of HA particles.Immersion tests show that average corrosion rate of Mg-2Zn-0.5Sr/HA composites decreases from 11.7 to 9.1 mm/year with the addition of HA particles from 0 wt% up to 0.3 wt%.Both microstructure and mechanical properties can be attributed to grain refinement and mechanical bonding of HA particles with second phases and α-Mg matrix.Bio-corrosion behavior can be attributed to grain refinement and the formation of a stable and dense CaHPO4 protective film due to the adsorption of Ca2+ on HA particles.Our analysis shows that the Mg-2Zn-0.5Sr/0.3HA with good strength and corrosion resistance can be a good material candidate for biomedical applications.