With rapid development of lithium ion batteries (LIB) and sodium ion batteries (SIB), hard carbon (HC) as new anode material has earned much attention. Besides its rich precursor sources and low cost, HC has higher Li⁺ storage capacity and better rate performance than graphite for LIB. Furthermore, it is also recognized as the most commercially potential anode material for SIB. However, low initial Coulombic efficiency is a common issue for HC. In addition, it is believed that the specific capacity can be further improved with the clarification of the Li/Na ion storage mechanism. In recent years, many researches on electrochemical mechanism have been conducted with some model assumptions proposed for better understanding the mechanism. This review introduced the structures and preparation approaches of HC as well as its application in LIB and SIB. The advantages, especially in fast charging, coating and other subdivision were discussed, and the different modification strategies such as pore structure design, doping, optimizing interface between electrode and electrolyte were summarized, aiming at the increase of capacity and the improvement of Coulombic efficiency of batteries.