Abstract: This study describes optimization of damper system design for pounding between existing building and its extension. In this system, passive coupling method is known to be an effective method to reduce undesirable vibrations and structural pounding effects and passive viscous dampers are used by which the existing building is connected to its extension. In this study, pounding Effect between existing building and its extension is studied by non-linear dynamic analysis. Firstly, the required ground motion records are o¬btained from PEER ground motion database by using input parameters. Secondly, the adjacent two buildings are separately analyzed and the maximum displacements of two buildings at connecting corner points are resulted.