It is of great importance to prevent catalysts from aggregating in order to maintain their high activity and stability for various applications. Based on a typical sacrificed SiO₂ template route, gold nanoparticles (AuNPs) stabilized on an Fe₃O₄@SiO₂ surface were anchored onto the inner layer of a polyaniline (PANI) shell, endowing a protection effect to avoid direct contact with the aiming molecules. The existence of the Fe₃O₄ core allowed the facile recycling of the catalysts from the reaction system. Compared to the sample without the protection of the PANI shell, Fe₃O₄@Au–PANI presented a much higher catalytic stability using the reduction of 4-nitrophenol by NaBH₄ as a model reaction.