(A)bstract-This study was carried out to investigate the mechanism and effects of experimental factors on the particle size distribution and particle morphology of synthesized precipitated CaCO3 in the carbonation process in which CaCO3 is formed by blowing rate Of CO2 gas into lime milk. The changes of pH and temperature occurred during the carbonation process for determining the dependence of the reaction completion time on experimental factors such as reaction temperature, initial concentration of lime milk and volumetric blowing rate Of CO2 gas. The synthesized CaCO3 powder was pure white calcite crystal of cubic shape with a median diameter of 0.75 mum. The reaction completion time was directly proportional to the initial concentration of Ca(OH)(2) in slurry above 0.5 wt%. The observed dependence of reaction completion time on the initial slurry concentration and the blowing rate Of CO2 gas could be qualitatively interpreted in terms of the proposed formulation for the carbonation process, which was constructed on the basis of the concept that the rate of Ca(OH)(2) dissolution is balanced by the rate Of CO2 absorption and by the carbonation reaction in an aqueous slurry containing fine Ca(OH)(2) particles.