Ever growing urban society increased the importance of lifelines on public life. One of the most important lifelines is buried pipelines transmitting Water and Gas. Most important cause to damages to pipelines is permanent deformations due to ground excitations. Deformations can be categored transient and permanent. Transient displacements occur due to wave effect and permanent deformations occur due to geotechnical events such as liquefaction and fault action. The liquefaction is reported as the major cause damages pipelines during and after earthquake. To evaluate seismic behavior of buried pipelines subjected to large deformation, appropriate none-linear cyclic stress-strain relationship should be implemented in any numerical method. Among the phenomena, witch cause permanent ground deformation, the settlement and lateral spreading induced by liquefaction are considered as the main cause of damage in buried structures. Therefore, this study is aimed to take into account the potential of liquefaction during an earthquake into numerical analysis of buried pipelines using FEM. During the earthquake, the soil volume and also pore-pressure water is changed therefore as saturated loose sand undergo simple shear deformation, the stiffness at any time is changed as function of the mean normal effective stress. In this study, a hypo-elastic model is adopted for the soil to evaluate changes in the pore-pressure and also effective stresses during the excitation. In a finite element modeling, for the areas not expecting liquefaction to occur the pipe is modeled using beam elements and soil is modeled by some bi-linear springs; while for liquefied areas, the pipe is modeled by shell elements and solid elements are used to model surrounding soil.