<p>Porous SiC has attracted extensive attention for its wide applications, especially in harsh environment, due to its unique properties. In the present paper, novel macro-meso-microporous SiC ultrathin fibers (MMM-SFs) were synthesized through electrospinning process associated with polymer-derived ceramics route, and the porous structure in the SFs can be conveniently tailored by tuning the composition of the spinning solvents and the concentration of the precursor (polycarbosilane). The surface features and microstructures of the resultant MMM-SFs were characterized in detail. These fibers presented a high specific surface area of 86.1–128.2 m<sup>2</sup> g<sup>−1</sup>. The formation mechanism of hierarchically porous structure was discussed as well. <i>N,N</i>′-dimethylformamide (DMF) played a critical role in forming macropores, while the decomposition of SiO<sub><i>x</i></sub>C<sub><i>y</i></sub> phase was responsible for the meso-/micropores. Our method utilized to synthesize hierarchically porous SFs is easily capable of designing other ceramic fibers.</p
