Mg-Zn-Ca alloys are expected to be widely used in human bone tissue implant materials due to its excellent mechanical properties, good biocompatibility and excellent degradability. However, the poor bio-corrosion resistance of magnesium alloys limits its further clinical application. The surface of Mg67Zn28Ca5 alloys with eutectic composition was modified by laser amorphization. The effect of laser scanning speed on the microstructure and phase composition of Mg67Zn28Ca5 alloys amorphous coating were studied. The bio-corrosion behavior of the alloy surface before and after laser amorphization in artificial body fluid was tested. The results show that a large amount of amorphous and a small amount of crystalline materials were formed on the surface of the specimens after laser amorphization. With the increase of laser scanning speed, more amorphous phases were formed on the alloy surface. The formation of crystal phase was mainly caused by thermal activation due to the thermal influence of subsequent laser processing, and some amorphous phases nucleated and grew up. Compared with the as-cast magnesium alloy, the corrosion potential of the amorphous layer in the artificial body fluid was positively shifted by 0.16 V, and the corrosion current density decreased about 13 times. The existence of a small amount of crystalline phase on the alloy surface became an active channel form surface corrosion, which had a slight impact on the corrosion performance of the alloy surface. The biological corrosion resistance of Mg67Zn28Ca5 alloy can be effectively improved by laser amorphization treatment, which shows a good application prospect in biomedical implants.