The seismic behavior of cable stayed bridge with 1255 meter span has been studied in this paper. A Finite Element model (FEM) has generated and the behavior of the bridge under ground motion has investigated, considering large deformation. The torsion can be occurred in the deck and other components of the bridge due to collision of seismic waves in direction expect of orthogonal directions of the bridge. Thus in this study, the effect of collision of seismic waves to the piers and abutment with different angle, has studied using the explicit dynamic analysis. Due to long distance of towers from each other seismic waves in from of uniform and non-uniform ground motion of the supports, have applied to the model. Moreover, local post-buckling behavior of the deck for different seismic loads has studied on the basis of geometric nonlinearity,. The results show that the top and bottom steel plates of the box girder, experience the post-buckling behavior and different responses can be obtained due to different strike angle with uniform and non-uniform support excitations. It shown that the study of long-span cable-stayed bridges under different strike angle of earthquake waves has necessity, and more economic sketch can be obtained with use of post buckling capacity.