Abstract: In order to improve the dispersibility of superfine calcium carbonate in PP, titanium titanate TMC-105 and stearic acid were compounded in different proportions, and the effect of different compounding ratios on the dry modification effect of ultrafine calcium carbonate was studied. And through the oil absorption value, activation degree and contact angle measuring instrument, Fourier transform infrared spectrometer, thermogravimetric analyzer and field emission scanning electron microscope to analyze the modification effect and modification mechanism of calcium carbonate; modified calcium carbonate filled PP Calcium carbonate/PP composites were prepared, the effects of single and compound modification on the mechanical properties of the composites were studied, and the dispersibility of calcium carbonate in PP was observed with a scanning electron microscope. The results show that the optimal dosage of single modification of titanate TMC-105 and stearic acid is 1.5% and 3% of the mass of calcium carbonate, and the optimal ratio of compound modification is 35% stearic acid + 65% TMC-105. After the single modified and compound modified calcium carbonate filled PP, the mechanical properties of the composite materials were improved, and the compound modified mechanical properties were the best. Its tensile, bending and impact strengths were higher than those of the unmodified calcium carbonate/PP compound. Materials improved by 19.4%, 22.6% and 51.5%. The compounded modified ultrafine calcium carbonate has the best dispersibility in PP, and basically no agglomeration occurs.