Abstract: Influence of boundaries of centrifuge model on the behaviour of pile groups with dumbbell shaped pile-cap supporting for a super large bridge was analyzed with 3-D elastic-plastic FEM.It was shown that the influential zone of vertical deformation of soil around pile groups and the influential thickness of compressive stratum under pile tips were approximately equal to the width of pile-cap and pile length respectively under the design load.The influence of boundaries of centrifuge model was small on the distribution and magnitude of the axial forces of pile group,but large on the deformation characteristics.