In response to the limitation of chemical flooding systems based on surfactants and polymers in enhancing oil recovery in high-temperature（＞100 ℃）and high-salinity（＞22.5×10⁴ mg/L）channel sand reservoirs，it was proposed to modify nanomaterials to simultaneously improve water flooding sweeping efficiency and microscopic oil washing efficiency. Firstly，the chemical modification of nano-SiO₂ was carried out，then the ability of modified nano-SiO₂ to form viscosity increasing emulsion with crude oil，the ability to reduce interfacial tension and the feasibility of enhancing oil recovery under heterogeneous conditions were studied. The experimental results showed that the modified nano-SiO₂ had a surface branching number of 10⁵. The modified nano-SiO₂ could form viscosity increasing W/O emulsion with crude oil in the water cut range of 10%—80%，and the viscosity of emulsion was 2—10 times of the viscosity of crude oil. Modified nano-SiO₂ could reduce the interfacial tension between oil and water to 10^-3 mN/m. Modified nano-SiO₂ in porous media improved macroscopic sweep efficiency through flow control and Jamin effect，and enhanced microscopic oil washing efficiency by reducing interfacial tension. After water flooding to a water cut of 98%， modified nano-SiO₂ flooding and subsequent water flooding could enhance oil recovery by more than 25% percentage point. All experimental results indicated that the tackifying active nano-SiO₂ was feasible for improving oil recovery in channel sand reservoirs.