Polyaniline nanofibers were facially synthesized by the chemical polymerization with binary oxidant containing ammonium persulfate and ferric chloride at the presence of para-phenylenediamine. For a better comparison, the polymerization with single oxidant was also carried out. The effect of binary oxidant on the morphology and structure was systematically investigated for better understanding the role of oxidant in the formation of nanostructures. The morphology, chemical structure as well as crystalline and thermal property were characterized by field emission scanning electron microscopy, ultraviolet-visible absorption spectroscopy, Fourier transform infrared and Raman spectroscopy, X-ray diffraction and thermogravimetric analysis.