Abstract: Although radiographic testing determines the nature of disfigurement through image on film, however usually, it cannot identify parameter of vice correctly, such as height and depth, and it has certain effect for practical work. This essay afforded a method of measuring height and depth of defect through the character of image on film using geometry principle. At the same time, the paper revised appropriately horizontal position of imperfection according to the character of image. Eventually, it proved further applicability of the means through specific example.