Commercial sedimentation CaCO3 was ground by a vibration rod mill to investigate the physicochemical properties of mechanically activated CaCO3.When the CaCO3of the calcite structure was ground, the intensities of the crystal facesof calcite was decreased by distortions and so on, and the aragonite appeared as the grinding proceeded. The formed aragonite was transformed to the calcite when the sample was heated at 773K for3.6 ks. The dissociation pressure of CO2 of the ground CaCO3was larger than that of the non-ground CaCO3.The enthalpy; entropy and specific heat of change of the dissociation reaction were obtained. At high temperature, the emission rate of the ground CaCO3 was slightly larger than that of the non-ground CaCO3. At room temerature, the CaCO3 adsorbs CO2, and it desorbs the adsorbed CO2. The amount of adsorbed CO2 on the ground CaCO3 was larger than that of the non-ground CaCO3.