Mg-Zn-Ca alloys were prepared by a casting technique, and some of as-cast alloys were solution treated at 470 oC for 24 h. The corrosion resistance of the alloys in simulated body fluid was investigated. The results show that positive shift occurs in the electrochemical corrosion potential of solution treated alloys in the simulated body fluid (Hank’s). And the resistance to soak corrosion is also greatly improved. The maximum corrosion rate of as-cast alloys is 5.3265 mm/a in the simulated body fluid. After solution treatment the rate is reduced to 0.8632 mm/a. It indicates that after solution treatment, the alloy shows a better corrosion resistance