Nowadays, with the advancement in software engineering and its application, the field seismic soil-structure interactions becomes an active research area and take the interests of many researchers in the field of structural and geotechnical engineering. A clear understanding of the effects of different parameters like pile diameter, length, spacing, raft thickness, and load level, and how they responded to seismic action involving the complex soil-structure interaction is the main concern of this thesis. Finite element based software, PLAXIS 3D CE V20, is used as a numerical modeling tool which is capable of capturing the different interaction among pile to the soil, pile to pile, pile to raft, and soil to raft. The reliabilities of the numerical results are validated with related prior works in centrifuge experiment and numerical modeling results. Boundary, Mesh size, and raft thickness sensitivity analyses are studied. The results on differential settlements, shows that some combinations of pile length, pile spacing and pile diameter provide relatively minimum differential settlement as one affects the other in the combinations which indicate requirement of optimization during design of PRF in seismic region. In general, for pile diameters considered, the longest pile length shows maximum horizontal displacement at raft center of piled raft foundation system which occurred around the sixth seconds of the dynamic time. However, unlike pile length, pile spacings considered in this thesis has negligible effect on maximum horizontal displacement during dynamic time. Moreover, results of the effects of the parameters considered in this thesis on pile total axial and skin friction forces, maximum bending moments in piles, and coefficients of piled raft foundation is discussed in details. For pile diameter of 0.75 m, the maximum bending moment in piles decrease with increase in pile length for all spacings considered throughout the dynamic time. In addition, the coefficients of piled raft increase with increase in pile length from 15 to 30 m. However, for the case of pile diameter 0.40 m as there is no clear pattern with this regards due to pile to pile interaction as piles are closer. Moreover, the piles located on forefront corners and the opposite side corners exhibit maximum negative and positive bending moment whereas, the middle piles shows relatively reduced bending moments. That is, increased pile diameter should be considered in these locations during piled raft foundation design in high seismic regions.