Abstract: Civil engineering structures in earthquake-prone regions should be designed to adopt the effect of an earthquake. The dynamic behavior of a building when an earthquake is shaking, depends on the variation of the parameters of the building structure, namely the mass, stiffness and damping value. The purpose of this study is to explore the effect of variations in the mass, the stiffness and the damping value to the dynamic behavior of a five-story building. The modal analysis method is applied to this study to calculate the modal parameters of the structure that are modal periods, modal damping ratios and modal participation factors. This study shows that variations in the mass and stiffness of the building have an influence on the modal periods, modal damping ratios and modal participation factors at various levels. The variation of damping values of building stories affects the modal damping ratios but does not affect the modal periods and modal participation factors.