Calcium carbonate (CaCO3) was synthesized by means of ultrasonic process in the presence of the water-soluble polymer carboxymethyl inulin (CMI). Synthesized CaCO3 crystals were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and BET (Brunauer, Emmett and Teller) isotherm. Applying Box-Behnken experimental design, the effects of the amplitude of sonicator (Amp), biopolymer concentration (BC) and the application time of ultrasound (AT) on the preparation of CaCO3 with respect to specific surface area (SSA) of final product was investigated. The experimental design was studied at three levels. The range of the amplitude of sonicator, polymer concentration and the application time of ultrasound were 25 %-50 %, 0.25-0.75 g/L and 1-5 min, respectively. The model equation representing specific surface area (SSA) of calcium carbonate was expressed as functions of three operating parameters namely the application time of the ultrasound, the amplitude of sonicator and polymer concentration. The results showed that the application time of ultrasound was the most significant variable that influenced the surface area of the crystals among three variables and the experimental results were in good agreement with those predicted by the proposed regression model. The highest value of specific surface area was obtained at the maximum application time of ultrasound.