In this paper,the structure of assembly foundation oferosion protection,its design and construction procedure are studied.Itis the development of double wall steel open caisson and reinforcedconcrete open caisson.Based on the data collected in tests,some difficultproblems about the principle of expanding foundation erosion prote-ction in deep water and construction methods are resolved.Comparedwith other foundations,the assembly foundation narated in this papercan decrease the time limit and construction cost of a project.Themethod may de better for solving the problem of bridge foundation indeep water.