A facile method for the preparation of porous ultrafine nanofibers was demonstrated. The PAN/NaHCO(3) composite nanofibers were electrospun, and then NaHCO(3) was removed by a selective dissolution and reaction with the solution of hydrochloric acid (10 wt%). The obtained PAN fibers showed highly porous surfaces after the extraction of NaHCO(3). The structure and properties of ultrafine PAN nanofibers were characterized by Fourier transform infrared (FT-IR), X-ray diffraction (XRD), and thermogravimetry (TG). The results indicated that NaHCO(3) could be introduced into the PAN solution and successfully electrospun. CO(2) is released and pores are formed on the fibers. The morphology image of the fibers was detected by scanning electron microscope (SEM) and showed that many pores aligned the nanofibers. Copyright (C) 2008 John Wiley & Sons, Ltd.