The objective of this report is to propose a non-linear response analysis method in frequency domain based on the stress and strain relationship of soil in frequency domain. First of all, a new model for the strain and frequency dependent characteristics between shear modulus and damping constant with respect to the complex shear modulus is proposed, considering the following two characteristics; One is the similarity of stress-strain relationship between time domain and frequency domain. The other one is a non-stationary characteristics in frequency domain caused by non-linearity of soil. A new non-linear dynamic response analysis method in frequency domain is proposed by incorporating the new model of the stress-strain relationship in frequency domain into the commonly used nonlinear response analysis method in frequency domain. The accuracy of this method is evaluated by the comparison of the analytical results obtained by two kind of non-linear dynamic response analysis codes. Hence, “YUSAYUSA2” and “SHAKE” is used as the co de in time domain, in frequency domain respectively. It is found that this proposed method is useful to take into account of nonstationary behavior caused by non-linearity of soil
