Abstract: 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.