The development of structure/function integrated materials is an important trend in military field. Herein, a hierarchical structure was introduced on carbon fiber surface via the successively grafting of polyacrylic acid (PAA) layer and Fe3O4 nanoparticles. It is found that this hierarchical structure could simultaneously improve the composites interfacial strength (30.5%) and toughness (82.6%), due to the mechanical interlocking by Fe3O4 and polarity matching by PAA layer. Moreover, for fiber's microwave absorption (MA) performance, the introduced magnetic Fe3O4 nanoparticles facilitate the impedance matching and magnetic loss, and large number of dipoles from PAA provide polarization loss for microwave dissipation, and finally lead to enhanced MA properties with strong absorption (-40.6 dB) and a wide effective bandwidth (6.13 GHz). In all, the present study offers a facile strategy for the preparation of structural/microwave-absorbing integrated carbon fiber, and could further provide guidance for other carbon fiber-based multifunctional materials. (C) 2021 Elsevier Ltd. All rights reserved.