Abstract: In this paper, the optimal ranges of the yield shear coefficient and the second isolation period are discussed by seismic analysis of structures excited by earthquake ground motions. The largest dissipative energy scale factor is used as the objective function, and constraint conditions include maximal sliding displacement of base-isolated layer, residual displacement and maximal base shear coefficient. It is found that the optimal range of shield shear coefficient relies on earthquake sites and earthquake amplitudes. The four earthquake response indexes for second isolation period are basically in uniform variation under four different sites and earthquake amplitudes. The proposed range of the second isolation period is from four seconds to six seconds.