In order to modify and optimize the performance of cement-based sealing materials and improve the gas drainage rate of boreholes. In this paper, nanosilica (NS), multiwalled carbon nanotubes (MWCNT), and graphene oxide (GO) were used to modify cement and optimize the pore structure. Uniaxial compression tests, X-ray diffraction (XRD), nuclear magnetic resonance (NMR), and combined fractal theory were used to analyze the mechanics and pore characteristics. The results show that the synergy of the three nanomaterials promotes the generation of hydration products such as calcium silicate hydrate (C–S–H) and ettringite (AFt), improves the total pore fractal dimension ( D w ) and seepage pore fractal dimension ( D s ), and optimizes the microscopic pore structure. However, when the content of NS increases from 2 to 4 wt %, the improvement in the mechanical properties is obviously weakened. The best ratio is where the SiO 2 content is 2 wt %, the MWCNT content is 0.1 wt %, and the GO content is 0.03 wt %. Compared with pure cement, the fractal dimension increases significantly, the mechanical properties are increased by 24.7%, and the total porosity is reduced by 23.9%. This paper is of great significance for improving the efficiency of gas mining.