Abstract: Owing to the effect of non-ideal factors in the imaging process, X-ray photographic image quality is degraded, resulting in a shift of image boundary position relative to that of the object. In this paper, the Monte Carlo method is used to simulate the flash photography process, and the influence of fuzzy and scattering on the boundary detection is studied. The result shows that the relationship between the blur size and the boundary deviation is dependent on the material, density and size of adjacent layers; under the same object structure, the larger the blur, the greater the boundary deviation; when the object structure is different, the boundary deviation is also different with the same blur size. The greater the ratio of scatter to direct, the greater the effect of scattering on the boundary detection results. When the ratio is greater than 50, the boundary detection error caused by scattering is more than one pixel.