A novel design strategy for synthesizing hard carbon microspheres (HCMs) from a single source of sodium lignin sulfonate is proposed for a practical anode material of sodium-ion batteries. The HCM has an optimized microstructure, including an enlarged interlayer spacing and few defects, along with a low specific surface area. As an anode material of sodium-ion batteries, HCM is highly promising for practical applications because of its high capacity and reversibility.