Abstract: The settlement behaviors of pile group foundation have a close relationship to the ground strata and the interaction between foundation and superstructure. It is an important and complicated part in pile foundation calculation field. Based on a series of large scale mode tests on pile groups, the settlement behaviors of pile group foundation are revealed by the corresponding test data. Furthermore, some important problems to calculate the settlement of the pile group foundation are discussed , such as the calculation of the vertical stress, the compression layer thickness and the pile shaft compression for long piles. Finally , the solutions to these problem are presented.