Abstract: This is an article in the field of mineral materials.While titanate coupling agent JN-114 and aluminate coupling agent DL-411 were used as modifiers, the surface of heavy calcium carbonate was modified by dry method. The effect of surface modification on heavy calcium carbonate was studied by means of activation index and contact angle. The mechanism of surface modification was analyzed with infrared spectrum analysis, and its filled PP composite was studied. The results show that the best modification process of JN-114 is as follows: reagent dosage 1.0%, modification temperature 70 ℃, modification time 30 min, modified heavy calcium carbonate activation index 99.21%, contact angle 114.34°. DL-411 modification best process: reagent dosage 1.0%, modification temperature 90 ℃, modification time 30 min, modified heavy calcium carbonate activation index 100.00%, contact angle 121.70°. Infrared spectrum analysis showed that JN-114 and DL-411 both acted on the surface of heavy calcium carbonate by chemical adsorption, heavy calcium carbonate changed fromhydrophobicity into hydrophobicity. The surface modification of JN-114 and DL-411 can effectively improve the impact strength of PP composite. When the modified heavy calcium carbonate filling content is 20%, the impact strength of the composite reaches the best, which is 38.87% and 41.97% higher than that of pure PP, respectively.