CaO formed by decomposing CaCO3 at 1450℃ was ground in a vibrational mill, then the long-time ground sample was reheated at different temperatures. Inverse Gas Chromatography (IGC) was used to measure the variation of the sample’s surface free energy under grinding and reheating. It is concluded that the total surface free energy and the London dispersive component of the surface free energy increases with grinding, while the polar component first increases with grinding, and then decreases , and finally disappears. When the long-time ground sample was reheated, its total surface free energy decreases , among which the London component decreases , but the polar component appears again. CaO formed by decomposing CaCO3 at 1450 ℃ was ground in a vibrational mill, then the long-time ground sample was reheated at different temperatures. Inverse Gas Chromatography (IGC) was used to measure the variation of the sample’s surface free energy under grinding and reheating . It is said that the total surface free energy and the London dispersive component of the surface free energy increases with grinding, while the polar component first increases with grinding, and then decreases, and finally disappears. When the long-time ground sample was reheated , its total surface free energy decreases, among which the London component decreases, but the polar component appears again.