Polystyrene-block-polyethylene oxide) (PS-b-PEO) diblock copolymer was synthesized and incorporated into novolac resin to obtain the nanostructured phenolic thermosets with hexamethylenetetramine (HMTA) as the curing agent. The morphology of the thermosets were investigated by means of atomic force microscopy (AFM) and small-angle X-ray scattering (SAXS). it was found that long-ranged ordered nanostructures were formed after and before curing reaction. In views of the miscibility of the subchains of the diblock copolymer with the phenol-formaldehyde resins after and before curing reaction, it was judged that the formation of the nanostructures followed the mechanism of self-assembly. In the thermosetting blends, the PEO subchain of the diblock copolymer was miscible with phenolic thermosets after and before cuing reaction. Fourier transform infrared (FTIR) spectroscopy showed that the curing reaction significantly weakened the intermolecular hydrogen-bonding interactions between phenolic matrix and PEO subchins of the diblock copolymer. The nanostructured thermosets were subjected to pyrolysis (and/or carbonization) at elevated temperatures to obtain the nanoporous carbons. The hierarchical nanoporosity of the resulting carbons was confirmed by means of transmission electronic microscopy (TEM), field-emission scanning electronic microscopy (FESEM), and surface-area Brunauer-Emmett-Teller (BET) measurements.