Fluffy Poly(ortho-phenylenediamine) (PoPD) microspheres with an average diameter of $2{mu}m$ have been successfully self-assembled from PoPD nanospheres. The SEM images showed that their surfaces consist of highly oriented nanofibers. The molecular structure of the synthesized fluffy microspheres was characterized by X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), Fourier transform infrared (FTIR) and UV-vis spectra techniques. To investigate the self-assembly mechanism of PoPD fluffy microspheres, the effect of mediates and time on the morphology of the products was also studied. The morphological evolution process indicated that the fluffy microspheres originated from PoPD nanospheres, then nanofibers were grew on the surface. The strategy was facile, effective, and controllable for the self-assembly of conducting polymer micro/nanostructures.