To the problems of narrow water operation space and difficult navigation guarantee faced by the construction of breakwater at the mouth of the fjord.Taking a breakwater project as an example,this paper analyzes the plane layout plan and structural characteristics of the double door,adopts the construction technology of water and land combined with throwing and filling into embankments,which is comprehensively promoted by the underwater lifting method and the water end entry method,as well as reasonable navigation control measures.Through engineering practice,the above construction problems are solved to ensure the smooth implementation of the project.The research results show that compared with the design of a protruding breakwater,the island breakwater with double door layout has more advantages in improving navigation efficiency and maintaining self-purification of the water in the bay,which can provide reference for similar projects.