Bismuth silicate with two morphologies (nanoflowers/nanoplates) was successfully fabricated with silica aerogels via a hydrothermal method in polyvinylpyrrolidone (PVP)-mediated processes for the first time. The obtained nanomaterials were characterized using x-ray powder diffraction, scanning electron microscopy, the Brunauer–Emmett–Teller (BET) surface area analysis, and UV-vis diffuse reflectance spectroscopy. It was found that the concentration of PVP plays an important role in the formation of the hierarchical nanoflowers. The formation mechanism for this novel morphology was proposed on the basis of experimental results. Moreover, the photocatalytic performances of Bi2SiO5 nanoflowers/nanoplates were also investigated. The results revealed that Bi2SiO5 nanoflowers exhibited higher activity than Bi2SiO5 nanoplates due to its suitable morphology, higher BET surface area.