In this study, the effect of temperature treatment during the preparation process of calcium carbonate (CaCO3) nanoparticles was systematically examined for a drug delivery carrier. The CaCO3 powder was prepared by the precipitation method at different annealing temperatures. The morphologies, elemental compositions and crystal structures of the synthesized CaCO3 powder were analyzed by Scanning Electron Microscope/Energy-Dispersive Spectroscopy and X-ray Diffractometry (XRD), respectively. The result shows that the particle size increased with an increase in annealing temperature. Based on the crystal structure analyzed from XRD, the sample was perfectly matched with the calcite/vaterite polymorphs phases. The crystallite size and lattice strains of the CaCO3 powder were calculated from the full width at half maximum parameter. The results show that the increase in annealing temperature leads to an increase in crystallite size and a decrease in lattice strain. The CaCO3 powder has a dielectric constant of 6.0-6.8 that reduced with the increase in applied frequency. The crystal structure, crystallite size, lattice strain, and dielectric properties of CaCO3 powder are dependent of the annealing temperature. Such properties confirm that CaCO3 powder is suitable for drug delivery carrier application.