Abstract: The influence of different generation of poly(amidoamine) (PAMAM) dendrimers on the crystallization of CaCO3 in aqueous solutions was studied. Crystallization of CaCO3 in the presence and absence of half generation PAMAM dendrimers was carried out. Crystals of CaCO3 having different generations of dendrimers were analyzed by means of FTIR, XRD, SEM, respectively. The results showed that the crystallization of CaCO3 in the absence of dendrimer resulted in the formation of rhombohedral calcite crystals, and spherical crystals mixed of vaterite and calcite were formed in the presence of G 0 5, G 1 5, G 2 5 PAMAM dendrimers, and spherical varterite crystals were formed in the presence of G 3 5, G 4 5 PAMAM dendrimers. As the generation number of the PAMAM dendrimers increased from G 0 5 to G 4 5, the particle size of vaterite was decreased from (6 0±0 5)μm to (0 7±0 5)μm under the constant concentration of the —COONa unit of the PAMAM dendrimers.