Abstract: The calcite structure and the adsorption of water molecules as well as water molecule clusters on it were investigated using the CASTEP module, Materials Studio 6.1 based on the first principles of the density functional theory (DFT). Results indicate that the O site of calcite shows the highest activity in the reaction process, followed by the C and Ca sites; 1014 is the most stable cleavage plane, where the adsorption can occur between the water molecule and the Ca and O sites, and the O site shows a more stronger adsorption effect with the hydrogen bond formed through the H(H₂O)-O(CaCO₃) and H(H₂O) -O(H₂O) bonds. There are both hydrogen bonds between the water molecules, as well as the water molecules and calcite surface whose adsorption effects are mainly found to be the O site followed by the relative weaker Ca site.