In this paper, cobalt nanofibers with controllable diameters are prepared via electrospinning. The surface morphology and the magnetic properties of Co nanofibers are investigated by scanning electron microscope and vibrating sample magnetometer. The results show that the morphology and magnetic properties of Co nanofibers can be easily adjusted by controlling the parameters during the fabrication process, such as polyvinyl pyrrolidone ratio in precursor solution, the strength of the electric field, and the heat treatment process. By comparing the morphology and magnetic properties of Co nanofibers prepared under different parameters, an optimized electrospun condition is determined. Due to the quantum size effect, the coercivity of Co nanofibers has been greatly enhanced to 1016 Oe. (C) 2015 Elsevier Ltd. All rights reserved.