Hard magnetic PbFe12O19 nanostructures were synthesized via a simple and rapid microwave method. The effect of concentration, temperature and power on the morphology was investigated. The products were characterized by X-ray diffraction, scanning electron microscopy, and Fourier transform infrared spectroscopy. Alternating gradient force magnetometer shows ferromagnetic property of the hexa-ferrite nanostructures. In order to prepare polymeric nanocomposite, lead ferrite nanoparticles were added to cellulose acetate polymer. The results show that saturation magnetization of nanocomposite was decreased while coercivity was increased (due to dispersion of particles into polymeric matrix).