The fibular PANI/ nano-CeO2 composites were synthesized via chemical oxidation of aniline using nano-CeO2 as an oxidant, and nano-CeO2 was prepared by hydrothermal treatment. Sphere-like morphology and fibers of PANI/ nano-CeO2 composites were obtained. The resulting composites were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), Fourier transform infrared (FT-IR). The results showed that chemical bonds existed between two phases. The acid concentration and nano-CeO2 particles affected the crystallinity of PANI fibers. The morphology of PANI was formed from the ball gradually developing into the fibular with rising of acid concentration. The regular crystalline structure of fibular was easy to form with a reducing CeO2 particle size.