In this study, the change of periods of planar frames by considering the soil-structure interaction is examined. For this aim, 5 different soil classes which representing in Turkey seismic code are considered. In this study, the suitability of using simplified methods for free vibration analysis of structure-soil interaction was investigated. Free vibration analysis of a typical frame system was carried out with four different approaches for five different soil classes and the results were compared. In the first model, the soil was modeled with shell elements using SAP2000 software. In the second model, SAP2000 was used again, but the soil was represented by equivalent columns. In the third model, the frame and shell are modeled with the equivalent shear beam approach. Lateral stiffness matrices and mass matrices of this model were created by the help of SCILAB software and periods were obtained. The fourth model is based on the assumption that the structure and soil are uniform throughout the building height and soil layers.In the fourth model, a practical equation in the literature was applied to the sample and the natural vibration periods were obtained for five different soil classes. At the end of the study, the results were evaluated.