Sodium-ion　batteries　(SIBs)　with　low　cost　and　high　safety　are　considered　as　an　electrochemical　energy　storage　technology　suitable　for　large-scale　energy　storage.　Hard　carbon,　which　is　inexpensive　and　has　both　high　capacity　and　low　sodium　storage　potential,　is　regarded　as　the　most　promising　anode　for　commercial　SIBs.　However,　the　commercialization　of　hard　carbon　still　faces　technical　issues　of　low　initial　Coulombic　efficiency,　poor　rate　performance,　and　insufficient　cycling　stability,　due　to　the　intrinsically　irregular　microstructure　of　hard　carbon.　To　address　these　challenges,　the　rational　design　of　the　hard　carbon　microstructure　is　crucial　for　achieving　highperformance　SIBs,　via　gaining　an　in-depth　understanding　of　its　structure-performance　correlations.　In　this　context,　our　review　firstly　describes　the　sodium　storage　mechanism　from　the　perspective　of　the　hard　carbon　microstructure＇s　formation.　We　then　summarize　the　state-of-art　development　of　hard　carbon,　providing　a　critical　overview　of　emergence　of　hard　carbon　in　terms　of　precursor　selection,　microstructure　design,　and　electrolyte　regulation　to　optimize　strategies　for　addressing　practical　problems.　Finally,　we　highlight　directions　for　the　future　development　of　hard　carbon　to　achieve　the　commercialization　of　high-performance　SIBs.　We　believe　this　review　will　serve　as　basic　guidance　for　the　rational　design　of　hard　carbon　and　stimulate　more　exciting　research　into　other　types　of　energy　storage　devices.