Objectives: The purpose of this study was to identify the correlation between calcium in soft drinks and enamel remineralization. Method: Six soft drinks were used in this study. These were calcium milk, normal milk, calcium yoghurt, normal yoghurt, calcium orange juice, and orange juice. Enamel specimens which 300-400Vickers Hardness Number (VHN) were selected. These samples were immersed in each soft drink for 12 hours in an in vitro remineralization model. All specimens were processed for SEM image of the enamel surface. Results were analyzed by SPSS 13.0 package program. Results: Calcium milk was the most influential and normal yoghurt was the least to enamel surface. There was not significant difference according to calcium supplement in milk although the difference of enamel hardness was f13.4 in calcium milk, and Δf4.7 in normal milk (P>0.05). Other soft drinks showed a little change about calcium but they were insignificant. Demineralization effect was remarkably observed in calcium yoghurt (-Δf269.1) and this effect was confirmed by SEM images. In conclusion, calcium supplemented soft drinks had little influences to hardness of enamel surface.