Abstract: The construction of underwater positioning, navigation and timing (PNT) system is a necessary way for China to explore the vast ocean and build a strong maritime country. Underwater acoustic timing technology is a key technology in the underwater PNT system, which provides high-precision time reference for underwater equipment and realizes time synchronization of underwater equipment. The article describes the basic concept of underwater acoustic timing technology, summarizes the difficulties faced by this technology and the current research situation at home and abroad; introduces and analyzes its application and importance in the fields of marine science, marine resources development, underwater acoustic communication and networking, national defense and security; on this basis, it looks forward to the future development trend of underwater acoustic timing and related technologies.