With the pace of domestic harbor construction to overseas,the seismic stability problem of breakwater has become particularly prominent in high intensity earthquake area.But domestic references about how to analyze the seismic response of breakwater are insufficient.Based on FLAC-2D ,some remarkable problems about geometrical modeling,boundary condition and applying damping are discussed and results of seismic response analysis in the cases of foundation treated and untreated are compared,which can serve as reference for similar projects.