A hybrid technique to calculate the scattering of two dimensional large bodies with cracks is developed by combining high frequency approximation method and a numerical method.Using the equivalence theorem

the technique divides the total scattered field into two parts

and employs iterative physical optical method （IPO） for the scattering from the large bodies with the cracks filled with perfect conductors and the moment methods （MoM） to characterize the cracks.The generalized network principle is then used to deal with the coupling across the opening of the aperture.Some numerical results have been obtained

showing the feasibility of proposed method.