Silicon (Si)/carbon nanocomposites have attracted extensive interests as emerging electrode materials in lithium-ion batteries (LIBs) due to their numerous premium features of high capacity, good conductivity, excellent ductility and long cycle life. Herein, we introduce a novel nitrogen-doped porous carbon fiber framework entrapped with Si nanoparticles (Si@NPCNF) by an improved electrospinning strategy with an in-situ reaction bath of pyrrole as the special collector. It is interesting that the in-situ collected polypyrrole (PPy) coated Si/PMMA precursor fibers show uniform diameter around 1.2-1.5 mu m with three-dimensional (3D) interconnected porous structures. After heat treatment at 850 degrees C, the resulted Si@NPCNF nanocomposite with high porosity and large surface area, can effectively relieve the severe volume expansion of silicon to reduce the pulverization of Si anode during the discharge/charge processes. Furthermore, the thin N-doped carbon layer derived from PPy can largely improve the conductivity of Si anode and shorten the Li+ diffusion distance. Meanwhile, the 3D porous structure can efficiently prevent Si from directly contacting with electrolyte to improve the cycling stability of LIBs. Therefore, the Si@NPCNF nanocomposite exhibits outstanding electrochemical performance which delivers a high initial capacity of 1521 mA h g(-1) at 0.1 A g(-1), a good rate capability of 648 mA h g(-1) at 2 A g(-1) and excellent cycle stability of 515.5 mA h g(-1) after 200 cycles at 1 A g(-1), being promising as a high-performance anode material for lithium-ion batteries.