A new iterative strategy combining analytical Kirchhoff Approximation (KA) with the powerful simulation tool finite elementboundary integral (FE-BI) method is presented in this paper to study the interactions between an object and the underlying rough surface. This hybrid FE-BI-KA scheme is an improved and generalized version of MOM-KA. Instead of using MOM, FE-BI is used to model scattering from the above object with the original incidence and scattered wave by the rough surface as the exciting source. Whereas scattering from rough surface is studied by the classical KA in order to reduce the computation resource and time required