Abstract: Behavior of the large diameter rock-socketed CFST piles under lateral loads was studied based on field tests and numerical analysis for piles in harbour engineering.The horizontal capability and deformation of the large diameter rock-socketed piles were analyzed from the measured results of displacement and internal force of piles.The interactive behavior of pile-rock and the influence of backfilled sand on horizontal capability were also discussed.Using FEM and considering the properties of pile-soil interface,the test results were simulated and the reasonable socketed length was studied.