Mg-Zn-Ca alloys are expected to become a new generation of internal fixation materials because of their high specific strength and excellent degradability. However, the relatively poor bio-corrosion resistance of magnesium alloys limits its clinical application. The microstructure, physical structure and element distribution of the Mg67Zn28Ca5 alloy modified by laser melting treatment were studied. The bio-corrosion performance of that in simulated body fluid was also investigated. The results show that a melted layer with an average thickness of about 508 μm was formed on the surface of the alloy after laser surface melting treatment of Mg67Zn28Ca5 alloy; the average grain size of the melted layer is about 10 μm. Compared with the as-cast and solid-solution alloys, the corrosion potential of the melted layer in the simulated body fluid was positively shifted by 76 mV and 60 mV, respectively; and the corrosion rate of the melted layer is 0.0468 mm/a, which is reduced by 82% and 78%, respectively. The oxide film on the surface of the alloy was denser, which improves the corrosion resistance of magnesium alloy at the early stage. With the decrease of MgZn2 content and the size of the second phase, the degree of galvanic corrosion was reduced and the corrosion of α-Mg matrix phase was inhibited.