In order to smoothly promote the construction of the national key waterway project,the 12.5 m deepwater waterway project in the Yangtze River below Nanjing,technical difficulties and construction characteristics of the project need to be analyzed to provide technical support for the design and construction of the project waterway regulation.Based on the analyses of the characteristics of water-sediment movement and navigation obstacle in the engineering reach,combined with the complex natural environment and protection demand of this tidal and bifurcated reach,the technical difficulties faced by the engineering design were analyzed deeply as follows:further understanding of water-sediment movement and shoal-channel evolution rules of the tidal and bifurcated river,determination of channel regulation parameters,channel inlet choosing and shoal controlling engineering layout,restrictions of the stakeholder,and advanced structure of regulating structures developing.The main characteristics of engineering construction were analyzed:long mileage,wide construction points,large quantity and high construction intensity bring about great difficulty in management,prominent contradiction between construction and navigation,difficulty in construction accuracy control and quality detection under harsh water conditions,and high requirements for ecological environment protection.The achievements has been conducted to provide instructions for the technical breakthrough and managing innovation regarding to this project,as well as the technical references for the feasibility demonstration and establishment management of similar projects.