Density functional theory was employed to explore adsorption mechanism of benzoic acid and toluene molecules on calcite surface, and to analyze influence of polarity on the adsorption. It showed that benzoic acid was tilted adsorbed on CaCO₃(104) surface in the form of undissociated molecules and in monodentate mode, while toluene was parallel adsorbed. Geometrical structure of organic molecules changed significantly during the adsorption, in which the deformation of benzoic acid was much greater than that of toluene. Meanwhile, electronic structure of the adsorption system was also changed. During the adsorption of benzoic acid, Ca-O ionic bond and H-O covalent bond were formed. However, there was only weak hydrogen bond between toluene and CaCO₃(104) surface. Obviously, adsorption intensity of benzoic acid (polar molecule) on CaCO₃(104) surface is greater than that of toluene (non-polar molecule). It provided theoretical support for EOR and mineral flotation engineering.