Abstract: It is studied, with the analytic method and the MonteCarlo numerical simulation for the flash Xray radiography of the tungsten sphere, that the scattered exposure and its space distribution are influenced by the sphere radius, the configuration of cells in the sphere, and the distance between the back cone and the recording plane. The results show that the scattered component of exposure is not homogeneous in space and increase while the radius increases. Enlarge the distance from the back cone to the recording plane can mitigate this inhomogeneity. It can be confirmed that the back cone is the primary source of the scattered exposure, and that increasing the distance between the back cone and the recording plane can reduce the scattered exposure effectively.