Cubic shaped CaCO3 particles with mean size of 30-40 nm were prepared by intermittent carbonation process without any additives. It was found that the How rate Of CO2 has no distinct influence on the particle size in the range of 30-120 ml.min(-1) under conditions of 13degreesC and stirring rate of 680 r.min(-1). A further increase of How rate makes the particles larger. When CO2 flow rate is 70 ml.min(-1), a high agitation rate is in favor of the reduction of the crystal size in the range of 70-680 r.min(-1). When flow rate is 120 ml.min(-1), the particles prepared at agitation rates of 680 r.min(-1) and 280 r.min(-1) have similar sizes, while products prepared at 90 r.min(-1) have larger size.