Generally, the soil around the structure is semi-infinite media, and the influence of loads to soil far from the structure is negligible under static loads. Then the suppositional boundary could be adapted in the soil far from the structure when the soil-structure interaction is analyzed. By simulating the soil in finite region, the subject could be transformed to the analysis of system which is composed of structure and finite soil. But in the analysis of dynamic soil-structure interaction, the radiant wave from the structure would be reflected to the finite soil by the suppositional boundary and the radiation condition could not be satisfied, so the finite soil should not be simply intercepted. Aiming at this problem, all kinds of artificial boundary such as viscous boundary, paraxial approximation boundary, superposition boundary, transmitting boundary and viscous-spring boundary were put forward by scholars to deal with the wave reflection on the boundary of finite model. But most of these boundaries had the problem of instability and large angle incident.In the seismic analysis of high concrete dams in hydraulic engineering, the traditional model of fixed boundary with massless foundation were often adapted, and the radiation damping of foundation and the inhomogeneity input of wave-motion could not be took into account. In order to overcome the defect of traditional methods and to find a new simply and effective time-domain method to eliminate the influence of boundary reflection, a series of study work was carried out in the present paper.1. Comparison and study of the dimensional effect of viscous boundary, transmitting boundary and viscous-spring boundary are carried out, the minimum distance under required precision between each boundary and consideration point is obtained. Result shows that, the minimum distance is 1.5 times of wave origin size for viscous boundary, 0.75 times of wave origin size for viscous-spring boundary and 1 times of wave origin size for transmitting boundary.2. Aiming at the problem of baseline drift in the time history of velocity and displacement of seismic integration, a series of effective time domain corrector method is obtained.3. The combination between the viscous-spring boundary condition and the implicit finite element method is established, and is applied to the dynamic analysis of gravity dams and arch dams of hydraulic engineering.4. Based on the principle of remote artificial boundary and the method of incompatible mesh, a new time domain computational method of gradual enlargement mesh method is put forward, in which the influence of radiation damping of