The polyaniline (PAni)/Co(0.5)Zh(0.5)Fe(2)O(4) nanocomposite was prepared by an in situ polymerization in an aqueous solution. The products were characterized by Fourier transform infrared (FT-IR) spectrometer, ultraviolet-visible (UV-vis) spectrometer, X-ray diffraction (XRD) and transmission electron microscope (TEM). The average particle size of the PAni/Co0.5Zn0.5Fe2O4 was estimated to be about 70 nm by TEM. The reflection loss (dB) of the nanocomposite was measured at different microwave frequencies in X-band (8.2-12.4 GHz), U-band (12.4-18 GHz) and M-band (18-26.5 GHz) by radar cross-section (RCS) method according to the national standard GJB-2038-94. The results showed the reflection loss of the PAni/Co0.5Zn0.5Fe2O4 nanocomposite was higher than that of the PAni. The maximum reflection loss of the PAni/Co0.5Zn0.5Fe2O4 nanocomposite was about -39.9 dB at 22.4 GHz with a bandwidth of 5 GHz (full frequency width at about a half of the peak response). In conclusion, this sample is a good microwave shielding and absorbing materials at higher frequency. (C) 2010 Elsevier Ltd. All rights reserved.