The management of Pearl River estuary relates to water agency, ocean agency, land use agency, maritime agency and traffic agency. Due to the overlap in the management scope of the Pearl River estuary, the responsibility in estuary is unclear and the management is confusion over the years. How to define beaches, estuaries and seas scientifically is the key to administration according to law. The author verified a large number of the domestic and foreign legal definition and other relevant documentation to make a detailed discussion for the laws and regulations relating to the boundary between river and sea in estuary area.. It proposes some solutions accordingly, for the existing management problems.