The authenticity of dynamic finite element’s results has a close relationship not only with boundary condition and the inputted datum of seismic wave. This paper calculates seismic response of large slipmass under different boundary conditions and inputted datum with time history method. On the basis of the calculating results to analyze the impacts which arise from radiation damping and inputted elevation on seismic response of slipmass and the law of seismic response. The results demonstrate that the upper part of Shangtian-town large slipmass has large displacement response and small shearing strength; but the response of lower part is opposite to the upper. Viscoelastic boundary can reduce the seismic response of slipmass; and the change of inputted elevation of earthquake wave can produce considerable influence on seismic response. The simulative rationality of radiation damping of foundation and inputted elevation of earthquake wave can influence the objectivity of seismic analysis.