We report the fabrication of poly(2-acrylamide-2-methylpropanesulfonic acid) modified SiO2 (SiO2/PAMPS) nanoparticles as plugging agents in water-based muds (WBMs). SiO2/PAMPS nano particles were prepared by the copolymerization of 3-methacryloxypropyl-trimethoxysilane-functionalized SiO2 nanoparticles and 2-acrylamide-2-methylpropanesulfonic acid. These SiO2/PAMPS nanoparticles were found to exhibit excellent salt tolerance, thermal stability, and good compatibilities with polymeric additives commonly used in WBMs. The plugging capabilities of the nanoparticles were tested with filter cakes on a high-temperature, high-pressure filtration press. The results indicated that SiO2/PAMPS nanoparticles can effectively block the nanopores in filter cake. In addition, WBMs containing SiO2/PAMPS nanoparticles were found to exhibit excellent plugging properties both at ambient temperature and at 80 degrees C, demonstrating that these nanoparticles are promising plugging agents in WBMs for drilling in shale formations.