Abstract: Owing to their excellent cost-effectiveness, environmental friendliness, and abundant precursors, hard carbons (HCs) are recognized as potential anode materials for sodium-ion batteries (SIBs). The presence of graphitic domains, numerous pores, and disordered carbon layers in HCs plays a significant role in determining their sodium storage capabilities. Nevertheless, the complex microstructures of HCs primarily stem from the precursors. Therefore, in this review, we elaborated the influence of functional groups (including oxygen-containing functional groups and heteroatoms) and microstructures (including morphology and pore structure) of precursors on the physical and electrochemical properties of HCs. Additionally, the influences of carbonization conditions (including carbonization temperature, heating rate and atmosphere) on the microstructures and electrochemical performance of final HCs are also discussed. The strategies and insights provided in this review aim to guide the design of high-performance HCs for SIBs, and the methodology may also benefit other energy storage systems.