Research conclusions：It is critical to determine the reasonable center of form in rigid calculation. The pile should be arranged according to the reasonable coincidence of the center of form of reaction force and the center of form of pile foundation. The bore force situation of the pile foundation should be calculated under different load combinations. If the center of form of reaction force can not coincide with the center of form of pile foundation, the bearing capacity of the pile foundation should be calculated according to the eccentric load. The reinforcement pile cap's stiffness, soil constraint and torsion moment should be considered in flexible calculation. The vertical and horizontal bore force situation, moment of piles and foundation displacement obtained with finite element method can be compared with those by rigid calculation, which can provide the data for crack calculation and upper frame structure of pile.