A microwave absorption nanocomposite is prepared by polyaniline (PANI) coated Fe3O4 nanoparticles and polybenzobisoxazole (PBO), the latter being a conjugated polymer with high mechanical strength and outstanding thermal and oxidative stability. Fe3O4@PANI nanoparticles are well dispersed in the PBO matrix to form PBO/(Fe3O4@PANI) nanocomposite, which has excellent thermal stability (high char yield above 55 wt% at 800 degrees C under nitrogen). Attributed to the conductive polymer PANI as shell and the good compatibility of PANI with PBO matrix, PBO/(Fe3O4@PANI) nanocomposite with 8 wt% of Fe3O4@PANI exhibits a minimum RL value of -28.6 dB at 10.1 GHz and below -10 dB in 9.3-15.4 GHz at the film thickness of 3.5 mm. This demonstrated the potential applications of PBO/(Fe3O4@PANI) nanocompositeas a low-density microwave absorbing material in extreme environments. (C) 2016 Elsevier Ltd. All rights reserved.