Abstract: Three-dimensional carbon nanonetworks (3D CNNs) have interconnected conductive skeletons and accessible pore structures, which provide multi-level transport channels and thus have promising applications in many areas. However, the physical stacking of these network units to form long-range conductive paths is hard to accomplish, and the introduction of micropores and small mesopores is usually difficult. We report a simple yet efficient strategy to construct CNNs with a nitrogen-doped micro-meso-macroporous carbon nanonetwork using Schiff-base gelation followed by carbonization. Using a polyacrolein-grafted graphene oxide molecular brush as the building block and tetrakis (4-aminophenyl) methane as the crosslinking agent, the obtained molecular brush nanonetworks have a high carbon yield and largely retain the original morphology, leading to the formation of a 3D continuous nanonetwork after carbonization. The materials have a micro-meso-macroporous structure with a high surface area and a highly conductive N-doped carbon backbone. This unique structure has a large number of exposed active sites and excellent charge/mass transfer ability. When loaded on carbon cloth and used as the electrodes of a flexible supercapacitor, the CNN has a specific capacitance of 180 F g⁻¹ at 1 A g⁻¹ and a high capacitance retention of 91.4% after 10 000 cycles at 8 A g⁻¹ .