Aiming at the problem of complicated conditions and ultra deep water filling bag cofferdam construction,this paper introduces bag body positioning,cofferdam filling and subsidence control technology.Using design of steel pipe pile positioning,positioning water filling bag,underwater filling process,it is completed the cofferdam construction with an average depth of 20 m and 150 m in length in Caofeidian coal terminal project,which can provide the reference for the similar engineering construction.