In this paper, we discuss the construction technologies of rock-socketed bored piles (RCP)through silty clay layer without protection in part by steel protective pipe, which is considered as the most important and difficult part of the whole was demonstrated according to RCP construction practice in the Luotou watercourse sea tower construction work (199 m in height and 2 200 mm in diameter of RCP of the foundation)of the Zhoushan lsland-mainland transmission line interconnection project in China. The main technologies including the construction methods for punching technology, building of steel platform, configuration of protective slurry, quality control of RCP punched aperture, punching methods, the clearance of pits, the installation of steel reinforcement cages and underwater concrete pouring are also introduced.