The aim of this research is to investigate the effect of concentration ratio of sodium alginate-gelatin on the characteristics of microspheres. Microspheres were prepared with ionotropic gelation methods aerosolization technique with sodium alginate and gelatin as polymer matrixes, and calcium chloride (1.5 M) as the cross-linker, and then dried using freeze dryer. The concentration ratio of sodium alginate-gelatin that was used to make microsphere was divided into F1: 2.25:0.25%, F2: 1.75:0.75%, and F3: 1.25:1.25%. Resulting microspheres were characterized in terms of characteristics (yield, particle size, and swelling index). The result showed that there was an increase in yield and particle size, as sodium alginate concentration increased on formula. The statistical test showed the concentration ratio of sodium alginate-gelatine showed a significant meaning different from the yield and particle size. The swelling index shows that the swelling peak of microspheres became more quickly with increased sodium alginate concentration.