With two segments having different chemical or physical properties, janus particles have gained widespread attention in recent years. A fast assembly-disassembly side-by-side capillaries-based microfluidic system was designed for rapid and easy generation of janus particles with magnetic anisotropic properties. Two immiscible organic phases, among which one contained magnetic particles, were emulsified by a stream of an aqueous phase into janus droplets formed at capillaries' tips and transported after breakup by the continuous aqueous phase in an outlet tubing. Then upon downstream UV irradiation, droplets were hardened into solid janus microparticles containing magnetic particles in one of their two segments. By changing the flow rates of organic and aqueous phases, not only the overall size of janus particles but also the relative volume of the two hemispherical segments could be controlled. Generated janus particles were proved having magnetic anisotropy by their forced-driven rotation in an external magnetic field, which makes them potentially interesting materials in chemical and biomedical applications. (C) 2014 The Society of Powder Technology Japan. Published by Elsevier B. V. and The Society of Powder Technology Japan. All rights reserved.