Earth pressure distribution and variation on foundation bucket of bucket foundation breakwater were simplified to the plain strain condition and studied by FEM. The numerical investigation shows that the earth pressure on the harbor side surface outside the harbor ward side bucket increases significantly, however,earth pressure on surface outside the sea ward side bucket decreased significantly, they affected the stability of breakwater notably. In the middle of the partition, earth pressure changed invisibly, displacement of breakwater and soil was likely the same. Harbor ward inner wall of seaward bucket decreased and sea ward inner wall of harbor ward bucket increased to a certain extent. Then earth pressure distribution on each wall under limit stated was analyzed for simplified stability analysis.