Transition metal oxides applied as anode material for sodium-ion batteries have been widely investigated due to their high specific capacity, especially for Co3O4-related nanomaterials. However, its intrinsic low electronic conductivity and the aggregation phenomenon of commercial Co3O4 nanoparticles result in a low initially coulombic efficiency and the fading of cycle performance. In this paper, commercial Co3O4 nanoparticles/carbon composite nanofiber mats were synthesized by sol- gel electrospinning. When directly applied, such flexible negative electrodes as sodium-ion batteries, revealed high specific capacity and excellent rate performance simultaneously, which are not only attributed to the high electronic conductivity of carbon nanofiber mats that could enhance the ionic and electronic transport property, but also attributed to its three-dimensional fibrous network that could prevent the aggregation of commercial Co3O4 nanoparticles. Such a flexible, binder-free and high electronic conductivity negative electrode enables promising applications for large-scale energy storage and conversion.