A simple sonochemical route was developed for the preparation of gold nanoparticles/boron nitride sheets (AuNPs/BNS) nanocomposites without using reducing or stabilizing agents. Transmission electron microscopy, scanning electron microscopy, X-ray diffraction, and UV–vis absorption spectra were used to characterize the structure and morphology of the nanocomposites. The experimental results showed that AuNPs with approximately 20nm were uniformly attached onto the BNS surface. It was found that the AuNPs/BNS nanocomposites exhibited good catalytic activity for the reduction of H2O2. The modified electrochemical sensor showed a linear range from 0.04 to 50mM with a detection limit of 8.3μM at a signal-to-noise ratio of 3. The findings provide a low-cost approach to the production of stable aqueous dispersions of nanoparticles/BNS nanocomposites.