Flexible, heteroatoms-rich activated carbon nanofibers with fascinating cross-linked architectures are successfully gained in a facile and controllable way via electrospinning polyacrylonitrile (PAN) /dicyandiamide (DICY) composite nanofibers followed by carbonation and a CO2 activation process. The unique inter-bonded structures and heteroatoms contents could be easily controlled by adjusting the preoxidation temperature applied in the calcining procedure and the addition of DICY. Significantly, the resultant samples display hierarchical pores with micro/meso/macropores, abundant N, O species doped and unique fiber-fiber interconnections, which considerably boost the electrochemical properties. As an electrode material, the activated N-doped cross-linked carbon nanofibers (ANCLCNFs) show a high capacitance of 323 F g-1 with a current density of 0.5 A g-1, excellent rate capacity (230.1 F g-1 at 20 A g-1) and long-term duration (over 95% after 10000 cycles). Furthermore, the symmetrical supercapacitor delivers a maximum energy density of 14.3 Wh kg-1 at a power density of 162.5 W kg-1.