Nano calcium carbonate with uniform particle size and high dispersion was prepared by pressurized carbonization system. The effects of calcium hydroxide concentration, surfactant addition amount, reaction temperature and CO2 pressure on the size and dispersion degree of prepared nano CaCO3 particles were investigated. X-ray diffraction (XRD), scanning electron microscope (SEM), Zeta potential and Fourier transform infrared spectroscopy (FT-IR) were used to characterize the prepared nano CaCO3 particles. The results showed that the optimum conditions for pressure carbonization are Ca(OH)2 mass concentration of 2%, surfactant dosage of 3% (percentage of theoretical production of calcium carbonate), reaction temperature of 40℃ and CO2 pressure of 6 MPa, the average particle size of the cubed calcium carbonate was 117 nm, and the crystal type was calcite calcium carbonate. The addition of surfactant cetyl trimethyl ammonium bromide (CTAB) to the carbonization reaction increased the positive charge formed on the surface of CaCO3 to +37.7 mV and higher than the standard value of 30 mV, indicating that the prepared CaCO3 product has good dispersibility and stability. FT-IR and Zeta potential were used to characterize CaCO3 nanoparticles before and after the modification of CTAB, and the influence mechanism of CTAB on the dispersion of synthetic CaCO3 nanoparticles was discussed, providing a new method for the preparation of nano CaCO3 .