Abstract: The concepts and applications of developing Underwater Acoustic Sensor Network (UASN) were introduced. After a review of underwater acoustic communication and network in the past，firstly in view of network topology indicated that multiple hop peer-to-peer network is suitable for underwater network application. Secondly according to network protocol stack conception, illuminated the corresponding problems on each protocol layer in the UASN. Thirdly made a physical analysis for the special characteristics in the underwater channel and narrated the main technique challenge in the UASN. Next introduced the key components that the UASN comprise. Then provided an illustration of UASN concept by used “seaweb”as an example. Finally gave the perspective on development and application of the UASN in the future in China.