Self-supported porous carbon nanofibers (CNFs) network has been prepared by electrospinning technology assisted with template method. The as-prepared material is rich in sub-nanoscale pores and nitrogen and oxygen functional groups, which can serve as a fast conductive network with abundant electrochemical active sites and greatly facilitates the transport of electrons and ions. When the porous CNFs network is used as an electrode for supercapacitor in a three electrode system, it displays a high capacitance of 233.1F/g at 0.2A/g, and a capacitance of 130.2F/g even at 14A/g. It maintains a capacitance of 154.0F/g with 90.17% retention after 4000 cycles at 2A/g. Moreover, the assembled symmetric supercapacitor not only exhibits excellent rate capability and cycle performance, but also delivers an energy density of 4.17Wh/kg and a power density of 2500W/kg. The experimental results demonstrate that the prepared N, O co-doped carbon nanofibers with rich sub-nanoscale pores are a promising electrode material for high-performance supercapacitors.