Abstract: The mechanism of reducing the seismic responses of adjacent structures under earthquake by using passive coupling elements interconnecting adjacent structures is exploited in this paper. The control effectiveness by using visco-elastic damper and fluid damper is compared. The two adjacent structures are simplified into two single-degree-of-freedom systems, and the connecting visco-elastic damper is represented by the Voigt model and the connecting fluid damper is represented by the Maxwell model, respectively. The optimal values for the two kinds of dampers are determined under the two objectives that minimize the averaged vibrational energy of the primary structure or the total averaged vibrational energy of the two adjacent structures under stationary white-noise ground motion, respectively. Numerical results of three types of adjacent structures whose frequency spectral characteristics are different under El Centro 1940 NS, Kobe 1995 and Tangshan earthquakes are used to compare the control effectiveness of the two kinds of dampers. A discussion on the control effectiveness is carried out.