In this work, we report a facile method to generate core-shell structured Fe3O4@SiO2-Ag magnetic nanocomposite by an in situ wet chemistry route with the aid of polyvinylpyrrolidone as both reductant and stabilizer. This method can effectively prevent Ag nanoparticles from aggregating on the silica surface, thus resulting highly dispersed and small-sized Ag nanoparticles. The as-prepared nanocomposite is composed of a central magnetite core with a strong response to external fields, an interlayer of SiO2, and numerous highly dispersed Ag nanoparticles with a narrow size distribution. Furthermore, the Fe3O4@SiO2-Ag nanocomposite showed high performance in the catalytic reduction of 4-nitrophenol and could be easily recycled by applying an external magnetic field while maintaining the catalytic activity without significant decrease even after running 15 times. (C) 2012 Elsevier Inc. All rights reserved.