The study of physicochemical properties such as surface area, particle size and basicity of heterogeneous catalysts is in great interest nowadays. CaO yield a number of surface defects centers and these were important especially for heterogeneous catalyst. In this study, nano structured CaO was synthesized via hydration-dehydration method. The basic strength of the prepared CaO was also studied using simple back titration method with respect to the activation temperature. This result revealed that, the basic strength increases with the increasing of activation temperature. As the nano structured CaO were prepared, more surface cavity and defect were expected to be present and thus, exposing more O2- sites, which influences the basic strength. Finally it was found that nano structured CaO was successfully prepared, while compared to the commercial CaO have a better chemical properties for catalytic chemical reactions.