Because in fields such as communications, radar is an important application value, medium target scattering Integral equation method is strictly, because of its high precision, the calculated results as the target scattering analysis of medium main This paper, focusing on the medium target scattering integral equations efficient research Using the surface integral equation analysis of complicated target scattering, impedance matrix Z is a dense If the moment method is directly, requires a great deal of storage and computation, largely hampered 3d scattering problem solving electrically Using FMM algorithm, although the iterative process dramatically accelerated by calculation, vector matrix is greatly reduced In order to overcome the above problems, this topic is using a independent of the green's function approach mathematical ACA --