This paper investigates the effects of fumed silica (FS) and precipitated silica (PS) on rheological behaviors of Carbopol gel. The elasticity modulus, yield stress, and thixotropy of Carbopol gel can be improved efficiently with the addition of either FS or PS. When the nanosilica concentration was less than 4%, the particle size is smaller and more uniform for FS-modified gel than PS-modified gel, leading to a more dramatically enforced rheological properties for the former; when the nanosilica concentration was increased from 4% to 8%, PS forms large agglomerates and therefore improves rheological properties. Results of fourier transform infrared spectroscopy (FT-IR) and scanning electron microscope (SEM) show that FS has more hydroxyls on its surface than PS as well as better dispersion in water. Different interaction ways of FS and PS with Carbopol were related to various surface properties.