In this study, calcium carbonate crystals were obtained by mixing of calcium chloride and sodium carbonate in the presence of biopolymer, carboxymethyl inulin (CMI). The effect of the feed rate of reactant and the initial [Ca+2] concentration was investigated. The produced calcium carbonate (CaCO3) crystals were characterized by scanning electron microscopy (SEM), Fourier transform infrared spectrometer (FT-IR) and X-ray diffraction (XRD). In the presence of additive (0.5 g/L), the polymorph of the obtained calcium carbonate crystals changed from pure calcite to the mixture of vaterite and calcite. With adding of biopolymer, the crystal structure of calcite changed from cubic to dumbbell shape.