Urchin-like PANI microspheres with an average diameter of 5-10 mu m have been successfully prepared. Their surfaces consist of highly oriented nanofibers of approximate to 30 nm diameter and 1 mu m length. The solvent composition plays an important role in the formation process of urchin-like PANI microspheres. The structure of the products has been characterized by FT-IR, UV-vis, and XRD. To investigate the self-assembly of urchin-like PANI microspheres, the effect of polymerization time on the morphology of the products has been studied. The morphological evolution process indicates that the urchin-like microspheres originate from the self-assembly of nanoplates, which then grow into urchin-like microstructures with nanofibers on the surface.