The precise control of nanostructures, assembly processing, and the size of each component is important for the construction of integrated functional nanocomposites. In this paper, we describe a simple two-step method for the synthesis of novel flower-like nanocomposites (AuNPs/NiSiO) composed of well-dispersed and size-controlled Au nanoparticles (AuNPs) immobilized on hierarchically structured layered nickel silicate (NiSiO). The as-prepared AuNPs/NiSiO nanocomposites exhibited excellent catalytic activity in the reduction of 4-nitrophenol (4-NP). The experimental results proved that the size of AuNPs played an important role in enhancing the catalytic activity. In particular, there was no visible decrease in the catalytic activity of the reused catalysts even after being recycled five times. Therefore, the hierarchically nanostructured material can be a promising candidate as the catalytic support.