Three kinds of dimeric aluminates (2DH-306, 2DH-324, and 2DH-335) have been used for surface modification of calcium carbonate (CaCO3) particles. The dimeric aluminates were shown to have an appreciable coupling effect at the interfaces between the light calcium carbonate (L-CaCO3) and polypropylene (PP) in the blends by mechanical property study and SEM observation. In the 2DH-306 modified L-CaCO3/PP (25/75) system, the impact strength exceeded that of the nonmodified system by more than 30 kJ/m(2). X-ray study showed that the dimeric aluminates had a synergistic effect with L-CaCO3 on the formation of PP beta-crystal, which would exert an important influence on the elongation ratio at break for the L-CaCO3/PP blends.