Abstract: As an emerging porous polymer material, covalent organic frameworks (COFs) have shown great potential in the development of high-energy-density lithium battery separators due to their tunable pore sizes, abundant active sites, and excellent chemical stability. The unique periodic porous structure of COFs not only effectively promotes the infiltration and penetration of electrolytes but also enables the precise design of ion transport channels at the molecular/atomic level, significantly enhancing the ion conductivity of the separator. By adjusting the chemical composition of COFs, more active centers can be introduced for electrochemical reactions. This paper systematically reviews the structural design principles of COFs, focusing on the functional modification methods of COFs in lithium battery separators and their regulation mechanisms on the mechanical properties, thermal stability, and electrochemical performance of the separators. Finally, the challenges faced by COF-based lithium battery separators in practical applications are summarized, and the future development directions and application prospects are prospected.