Abstract: For the case of the multi-degree-of-freedom, viscous damping system subjected to seismic excitations, a formulation of optimizing Rayleigh damping coefficients is developed by using the objective function of the peak response error at certain degree of a structure. Then, based on the empirical equation of earthquake spectrum varying with damping ratio, the approximate solution on the derivation of response spectrum is obtained. Therefore, a formulation which includes the comprehensive effects of structural dynamic characteristics, direction and frequency content of seismic excitation is addressed. Finally, seismic responses of a high-rise building subjected to 10 earthquake waves are analyzed. Numerical examples demonstrate that the new method can reduce the numerical errors which are induced by the Rayleigh damping.