Abstract: Unlike a single circular pile,the pile group is non-axisymmetrical.Therefore,not only the pile spacing but also the pile group layout will have influence on both the bearing capacity and the pile group effect of pile groups.In order to analyze these influential factors,a calculation method was proposed for obtaining the load-settlement relationship of the pile groups with or without a rigid cap,using the Mindlin equation and the static force equilibrium equation.Additionally the proposed method could consider piles with unequal length and diameter.Compared with the existing methods,the proposed method could obtain more reasonable results which could decrease pile group effect and render a distribution of pile head load agreeable to the fact.It was also founded that the distribution of friction around pile section was unequal,and the friction on the internal piles was larger than that on the external piles of the group.