Nano-CaCO₃ with different particle sizes have different characteristics and application scopes.So far the method of controllable preparation for nano-CaCO₃ with required particle sizes has not been reported.The effects of different experimental conditions on the particle size were studied by double decomposition method with calcium chloride and ammonium carbonate as raw materials,and with ethanol,citric acid and sodium pyrophosphate as disperants.Based on the research results,nano-CaCO₃ with the average size range at 17~71 nm were synthesized and characterized.The experimental results showed that,the samples prepared were vaterite structure with high purity,and the shapes were approximately spherical.The preparation conditions and disperants had significant influences on the particle size of nano-CaCO₃.As the reaction temperature increased the diameter decreased;the diameter increased with the increasing of the dropping time;with the concentration of the reactant increased,the particle size decreased first and then increasd; when the disperant additive was a mixed solution of citric acid and sodium pyrophosphate,the particle size was the smallest;when the disperant was a mixed solution of ethanol and sodium pyrophosphate,the particle size was the largest.Utilizing these influence rules,the controllable preparation of nano-CaCO₃ with the required particle sizes can be attained by controlling the experimental conditions.