The　mathematic　expression　for　scattering　cross　section　in　inhomogeneous　material　is　deduced　in　this　paper.　Then,　the　quantization　of　Kramers-Kronig　relation　in　inhomogeneous　medium　containing　scatterers　and　non-chatterers　is　given.　Based　on　the　frequency　change,　the　phase　velocity　due　to　the　inhomogeneous　material　is　introduced　into　two-dimensional　Kirchhoff　approximation　formula.　Finally,　the　flaw　shapes　in　inhomogeneous　medium　is　reconstructed　by　using　backscattered　ultrasound　through　experimental　method.　The　results　verify　the　feasibility　of　flaw　scattering　theory.