Abstract: In order to eliminate the effect of scattered radiation in image reconstruction with the iterative method, it is necessary to design the layout and configuration of the high-energy flash X-ray radiography system with uniform scattering distribution. The definition of scattering uniformity is given and the optical path error produced by eliminating the effect of scattered radiation with average scattering exposure is analyzed. Various factors affecting the scattering uniformity are studied using Monte-Carlo method, including system magnification, radiographic distance and the distance between back protection cone and imaging plane. It is shown that a main factor affecting the scattering uniformity is the distance, which determines the shape of scattering distribution and scattering exposure