Hybrid cylindrical micelles loaded with nanoparticles are fabricated via extrusion of spherical micelles in solution phase through small long cylindrical pores. Small gold nanoparticles (AuNPs) are pre-coated with thiol-terminated polystyrene and then further encapsulated in the core part of block copolymer spherical micelles by a precipitation method. By varying the starting mass ratio of AuNPs and the diblock copolymers polystyrene-b-polyisoprene (PS-b-PI) during the encapsulation, the AuNPs loading density along the cylindrical micelles can be controlled. The mechanism for this sphere-to-cylinder transition induced by extruding hybrid spherical micelles through small cylindrical nanopores is discussed. These findings provide a novel way to manufacture high-quality and functional polymeric nanowires, which may open the door to new applications such as in plasmonic waveguides.