||This study introduces a facile and robust method for synthesis of amphiphilic monodisperse Janus microparticles with tailored surface-mediated catalytic activity. The Catalytic Janus microparticles were synthesized based on the seeded monomer swelling and consecutive polymerization. Through this technique, we can not only precisely tune the relative dimension ratio of the compartmented bulb against the whole particle, but also provide the amphiphilicity to the particles. In the continued study, we patch functional metal nanoparticles onto one of the bulb surfaces. Finally, using the metal-patchy Janus microparticles, we demonstrate that they are of great importance and play a role in the fields of catalytic chemical reactions and electromagnetics.