Composite non-woven mats of poly(vinyl pyrrolidone) (PVP), chitosan, and Fe3O4 were successfully fabricated using coaxial-electrospinning technique with PVP/chitosan as the shell and PVP/Fe3O4 as the core. Because of the templating and confinement properties of the nanofibers, magnetic chitosan nanoparticles (MCNPs) could be spontaneously formed through molecular self-assembly when the composite fibers were dissolved on treatment with acetum solution. By changing the weight ratio of Fe3O4:chitosan, the size of the MCNPs could be varied. The morphology, chemical composition, and magnetic characteristics of composite particles were characterized by means of scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction, and vibrating sample magnetometer. Experimental results indicated that the composite particles were super-paramagnetic with sizes in the range of 15-40 nm. This facile and new synthesis route comprises a convenient strategy to generate composite particles and should be broadly applicable to a wide range of systems, serving as a platform for the facile development of novel composite materials.