Polyacrylonitrile (PAN)/polyaniline (PANT) composite nanofibers with diameter about 500 nm were successfully prepared by electrospinning a precursor mixture of PAN and aniline (ANI), followed by slow oxidative polymerization of ANT with ammonium persulfate (APS) in aqueous solutions. Morphology and structure of the resulting PAN/PANT nanofibers were characterized by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR),X-ray diffraction (XRD) and laser Raman spectroscopy. The factors influencing the morphology,size and uniformity of the composite nanofibers as well as the impact of the content of PANI on the electrical conductivity of the composite nanofibers were discussed, respectively. The results demonstrated that the PAN concentration, content of ANT added and applied electric voltage were the main factors which may influence the properties of the composite nanofibers. Moreover,PANI was nanodispered in the PAN matrix. The PAN/PANI composite nanofibers possessed good electrical conductivity, and the electrical conductivity could reach 10(-2) S/cm,when the PANT content was over 18%.