Magnesium (Mg) alloys have been used for stent application since decade ago due to its biocompatibility. However, in chloride-abundant environment like human body, the degradation is considered too rapid. Alloying is one of options to reduce its rapid corrosion rate. Zinc (Zn) and Calcium (Ca) were chosen as alloying elements regarding their biocompatibility to human body, reduction in the corrosion rate and improvement on the grain size. The microstructures of three alloys Mg-1.0Zn-xCa (x=0.0, 1.0, 2.0wt) were studied by field-emission scanning electron microscopy (FESEM). Surface morphological analyses exhibited that the presence of Ca led to the uniformity and the formation second phase, reduction of grain size and the boundary more visible. © International Federation for Medical and Biological Engineering 2016.