With n-octyl triethoxysilane and 3-mercaptopropyl triethoxysilane as modifiers and hydrogen peroxide as oxidant, the surface of hydrophilic nano-SiO2 particles was modified in a water-based environment to obtain amphiphilic nano-SiO2 particles with sulfonic groups and octyl groups, and their chemical structure and thermal stability were analyzed by FT-IR and TG. The amphiphilic nano-SiO2 particles were dispersed in the formation water to prepare the nanofluid, and the stability, interface properties, and imbibition efficiency of the nanofluid were evaluated. Nuclear magnetic resonance technology was used to explore the migration rule of crude oil in core pores during the nanofluid imbibition. The results indicated that the nanofluid was stored for 30 d without delamination phenomenon and therefore exhibited good stability. The hydrophilicity of the core treated with the nanofluid was enhanced. Furthermore, the amphiphilic nano-SiO2 particles could reduce the interfacial tension to 1.7 mN/m. An imbibition recovery factor of up to 22.6% was achieved with the nanofluid. In the initial stage of the imbibition, crude oil in small pores was discharged, while in the later stage of the imbibition, crude oil in large pores was discharged.