The effect of the operating variables such as mean residence time, agitational speed and surfactant type, on the precipitation of calcium carbonate was experimentally investigated in MSMPR and Couette-Taylor reactors. The precipitates was produced by the gas-liquid reaction of CO₂ gas and Ca(OH)₂ aqueous solution. Under-fixed temperature and concentration in MSMPR reactor, it was founded that the surfactant type had the greatest influence on the mean particle size and this effect was represented numerically by the zeta potential. With increasing the impeller speed the mean particle size increased due to decrease of the resistance in mass transfer processes. The vortex flow in Couette-Taylor reactor affected the precipitation of calcium carbonate complicatedly. The homogeneous mixing owing to Taylor vortex in Couette-Taylor reactor led to the more uniform particle size distribution than that in MSMPR reactor.