Studying the behavior of landfills under earthquake conditions to maintain safety and prevent failure is of significant environmental importance. The purpose of this study is to investigate the effective parameters in the seismic behavior of landfills with a combination of laboratory, field, and numerical methods. In this regard, Kahrizak landfill center (KLC), located in Tehran, was selected as an example of landfills in developing countries to study different parameters.  At first, a series of field and laboratory experiments, including CSWS tests and cyclic triaxial tests were used to determine dynamic parameters of the municipal solid waste (MSW), including shear wave velocity, damping ratio, and shear modulus in the ages of fresh, 7.5, and 16 years old. Then, using the available results, the one-dimensional equivalent linear analysis was performed by DEEPSOIL software to model the landfill behavior under different seismic accelerations. The effects of waste aging, types of foundations, the height of landfills, and seismic base accelerations on the dynamic response of MSW are presented in terms of peak ground acceleration, displacement, and stress ratio. The results of these studies showed various effects of the parameters on the landfill seismic behavior. Landfill behavior is highly dependent on the components of waste and age changes. Thus, the increase in the waste age and the process of decay can increase the surface acceleration and, ultimately, the resonance phenomenon in 7.5, and 16 years old samples.