The pile-based gravity support structure consists of a gravity chest wall and a double-row pile,is a semi-rigid semi-flexible support structure.For the design of the structure,the relevant unit reference specification uses the plane steel frame elastic fulcrum method to calculate the lower double-row pile,at the same time the upper chest wall is simplified as the cantilever beam for calculation.But the mechanical characteristics and the constraints on double-row piles are different from that of the cantilever beam because the chest wall is rigid body.In order to systematically study the deformation and internal force distribution characteristics of the structure in different calculation models,the normalized design and the calculation results of the solid model are compared.The results show that:according to the relevant specifications,the upper chest wall produces linear displacement,and the bending moment and shearing force of the rear pile are larger than that of the front pile;in the solid calculation model,the upper chest wall has a translational displacement pattern,so the bending moment and shear force of the front pile are greater than those of the back pile because the foundation pit excavation is affected by the main earth pressure difference.