We proposed a backward calculation method to identify the incident wave in time domain for applying non-linear analysis (Proc. JSCE, No. 577, 1997). In this paper, as an application of the proposed method, the incident wave is identified at Port Island from the measured acceleration at G. L. -83m. The numerical results show the accuracy and the utility of this method. In case of the non-linear dynamic response analysis for the soil system, the proposed method is more suitable for the identification of the incident wave than the equivalent linear method.