将不同粒径的SiO2微球与环氧树脂复合，制备用于直流特高压关键设备的高性能环氧绝缘复合材料，分析了其体积电阻率、介电常数与损耗，考察了SiO2微球对复合材料主要电气性能的影响；通过扫描电镜、动态热分析SiO2微球与环氧树脂的界面作用. 结果表明，不同粒径的SiO2微球均对环氧树脂复合材料性能有改善作用，添加100 nm SiO2的复合材料提升效果最显著，体积电阻率从1.87′1017 W×cm提至3.24′1017 W×cm，介电常数实部从10.99降至4.92，玻璃化转变温度从104.9℃升至106.4℃，这是因为100 nm SiO2微球表面吸附水分少、与树脂作用力强.

SiO2/epoxy composite was prepared with silica microspheres at different diameters as filler, which would be used in ultra high voltage DC transmission system. The effect of silica particle size on dielectric properties of the composite was studied by measuring DC volume resistivity, relative dielectric constant and dielectric loss tangent. The role of interface between silica microspheres and epoxy matrix was investigated using SEM and dynamic mechanical analysis. The results indicate that silica microspheres can significantly enhance the dielectric properties of the material. The composite with 100 nm SiO2 filler shows the best results. Its glass transition temperature and DC volume resistivity increase from 104.9℃ to 106.4℃ and 1.87′1017 Ω×cm to 3.24′1017 Ω×cm, respectively, while its relative dielectric constant decreases from 10.99 to 4.92.