Abstract: Based on investigations and model tests, and in combination with the research work on group effect for pile groups under lateral load relating to the code of fixed offshore platform, A series of studies ware performed oa behavior aad failure mechanism of laterally loaded pile groups, critical pile spacing on group effect, lateral bearing capacity of pile groups and its main influence factors, the stress-strain relationship for single pile and pile groups and so on. Some new laws about non-uniformity of load distribution ia the longitudinal direction of pile group and load-deflection (p-y) curves for pile groups were discovered, and the empirical formula was presented in order to remedy the defect of current calculating methods at home and abroad. These results can be provided as a reference for design of pile foundation under lateral load.