In　order　to　reestablish　the　linear　absorbing　coefficients　of　the　investigated　object　using　the　information　of　flash　radiographic　image,　some　image　restoration　procedures　for　a　correction　of　the　scattering　effect　are　required.　A　theoretical　model　precisely　calculating　uncollided　ray　and　the　once-scattered　ray　flux　of　the　detectors　was　established　based　on　analytical　method.　The　coefficients　of　the　secondary　scattered　ray　flux　were　also　corrected　by　Monte-Carlo　simulations　of　different　investigated　objects　using　the　MCNP　code.　According　to　the　above　method　an　efficient　analytic　photon　transport　calculation　code　SAT　was　developed.　Comparing　the　results　of　SAT　code　with　that　of　MCNP　code,　it　shows　that　the　SAT　code　outperforms　the　MCNP　code　in　terms　of　much　less　computing　time　with　comparable　precision.　It　provides　a　fast　and　precise　procedure　to　correct　the　scattering　effect　based　on　iterative　reconstruction　of　flash　radiography.