Based on scheme of Dalian gulf cross-sea bridge, in this paper, a 3-dimensional FE model for Self-anchored cable-stayed suspension bridge is established with finite element program and pile-soil-structure interaction is simulated by use of the equivalent embed fixation model. Based on the FE model, model analysis is carried out and the effects of pile-soil-structure interaction on dynamic behavior of long-span self-anchored cable-stayed suspension bridge are specially studied. Under vertical excitation, the seismic response analysis result considering that pile-soil-structure interaction was compared with that of without considering such interaction. The analysis result show that interaction reduced longitudinal displacement of stiffening beam in middle of main span and tower at bottom, moment at bottom of tower and auxiliary pier pile, but enlarged the moment of conjoining section between steel and steel beam. The research results provide some theoretical foundation to composite structure system.