Both NiO and hollow CO3O4 fibers with the diameter of about 10 mu m have been successfully prepared through spinning high viscous sols into precursor fibers and followed calcination process, The evolution process from precursor to crystalline fibers and the microstructures of the obtained fibers were characterized by TG-DSC, FT-IR, XRD, HRTEM, SEM and the like. The method is facile and cost-effective for mass production of fibers and the obtained fibers are pure phase with high crystallinity. Their magnetic properties were investigated, showing that both the fibers are ferromagnetic. Meanwhile, the NiO fibers exhibit good photocatalytic performance for the removal of Congo red from water under UV light irradiation. (C) 2015 Elsevier Ltd. All rights reserved.