Abstract: A three-dimensional numerical model for pile-soil interaction is established, based on studies of the bearing capacity of a super long pile under side and lateral loads. And the varying law of skin friction and moment of the super long pile is analyzed. The analysis results show that the increasing of the ratio k of the lateral load and the side load is effective in reducing the negative skin friction; furthermore, the critical ratio k is 4. The negative skin friction and moment decrease as a result of length-diameter ratio decrease. Moreover, the critical side load distance s is 8 m. When s 8 m,it almost has no effect on the negative skin friction. The bearing capacity of the super long pile can be effectively improved by decrease of stiffness ratio of the pile and soil. Meanwhile, by using multivariate nonlinear regression analysis, the expressions of the minimum skin friction on different factors are achieved. Then the minimum skin friction with different combinations of factors can be predicted by the expression. Thus the negative skin friction can be avoided effectively.