<p>Hard carbon, characterized by a unique turbostratic graphite domain structure, has become the preferred anode material for sodium-ion batteries due to its excellent reversible capacity at low potentials. However, achieving the directional design of pseudo-graphite structures by regulating the crosslinking density of precursors in hard carbon remains a major challenge in industrialization. In this study, a self-crosslinking polycondensation approach is developed to realize controllable microcrystalline hard carbon by the low-temperature hierarchical carbonization process of phenolic resin components. A three-dimensional crosslinked network composed of methylene and ether bonds was formed, which effectively inhibits the excessive graphitization of carbon domains and then optimizes the interlayer spacing and abundant closed-pore structures. The optimal hard carbon with low crosslinking density (HC-L) exhibits a high reversible specific capacity of 348.4 mAh g⁻¹ at 0.05 A g⁻¹ with a significantly improved rate performance (197.3 mAh g⁻¹ at 2.0 A g⁻¹), which is attributed to the unique crosslinked structure enabling HC-L with excellent sodium storage performance at low potentials. This study proposes a molecular-level regulation strategy to design the resin-derived hard carbon through controlling the crosslinking density, providing novel insights for the industrial development of state-of-the-art hard carbon materials.</p>