The objective of present paper is to develop the practical numerical analysis system for calculating responses of motion and mooring force on floating structures induced by tsunami in shallow sea region. In the present analysis system, incident wave profile of tsunami in shallow sea have been assumed to dispersed wave based on the data base of tsunami height in all over Japan. And more boundary value problem for dispersed wave have been analyzed by the boundary element method in time domain and also the responses of motion and mooring forces for floating structures have been calculated by convolution integral method. The numerical calculation by the present method have been carried out and the results by present method have been compared with the results by CADMASU-SURF based on NS equation and with the experiment results. From these comparisons, the authors have discussed as follows: 1) From above comparisons, the accuracy and the usefulness of present numerical method have been examined. 2) From the comparisons between the numerical results for dispersed wave and solitary wave, the deference for characteristics of motion and mooring force have been discussed