Abstract: To investigate the influence mechanism of nano-SiO₂ doping and its surface modification on the electro-thermo-mechanical properties of polypropylene, this paper adopts the molecular dynamics method to establish a silica/polypropylene composite model. Taking the SiO₂ particle size and the grafting rate of silane coupling agent KH550 on its surface as the variables, this paper studies the microstructures and electro-thermo-mechanical properties of the composite model at different temperatures. The results show that the properties of polypropylene composites are all enhanced after SiO₂ doping, but the degree of enhancement is different. Compared to other particle sizes, the 0.88 nm composite system has the most significant performance enhancement effect, with a 39 K increase in glass transition temperature, 27.39% increase in thermal conductivity, a decrease in mean square displacement and free volume, and a small increase in mechanical modulus and dielectric properties compared to polypropylene at room temperature. The composite system with 10% grafting rate of KH550 has the most significant effect in enhancing the electro-thermo-mechanical properties, with the thermal conductivity enhanced by 74.23% compared with polypropylene, and the enhancement of mechanical modulus and dielectric properties is more obvious. The results of the study can provide methodological guidance and reference for enhancing the electro-thermo-mechanical properties of polypropylene.