This study was aimed at addressing the present challenge in self-controlled catalysis, as to how to furnish smart catalysts with robust switchable ability in aqueous media. This objective was reached by developing a marine mussel-inspired polymer reactor that was capable of adapting to switch in aqueous media. This polymer reactor was composed of catalytic Au nanoparticles and a mussel-inspired polymer carrier that contained self-assembled switching interactions. The self-assembled switching interactions, by opening and closing, acted as a molecular switch for providing controlled access to the encapsulated metal nanoparticles, which caused switchable catalytic ability. In virtue of the mussel-mimicking functionality, the switchable catalytic behavior at this polymer reactor was repeatable and compatible with aqueous media, which involved neither hydrophilic/hydrophobic paradigm nor any leaching of metal nanoparticles. In this way, this polymer reactor demonstrated a robust switchable ability. This new protocol shows a promising prospect to develop robust smart catalysts for controlled catalytic processes occurring in aqueous media.