Basic Calcium Carbonate(BCC) is an unstable transition phase generated as a precursor when precipitated calcium carbonate is synthesized by a carbonation process, and it is generally synthesized at pH 13 or more. BCC is plate-shaped, and this feature is not seen in existing calcium carbonate, and has high functional properties as a filler or a coating agent for paper because of its characteristics of high whiteness, high capacity and low specific gravity. In this study, stable BCC was synthesized through electric conductivity and consecutive measurements of pH under a Ca(OH)(2) concentration of 3.0similar to5.0wt.%, reaction temperature of 10similar to20degreesC, and CO2(g) flow rate of 100similar to250 ml/min. Moreover, under the optimum conditions for a synthesis of BCC, the temperature of Ca(OH)(2) slurry was raised within a fixed heating rate from 15degreesC to 17, 19, 21 and 23degreesC, respectively, in the middle of the reaction. The experiment was conducted with elevated temperature being applied until the reaction was completed. Therefore, it was recognizable that the particle size of the final crystal was small at a high temperature when heated in the initial reaction stages, and it was large at a high temperature when heated by the same method for 30 minutes after the reaction was started.