The invention discloses a method for preparing an exposure curve for radiographic inspection. The method comprises the following steps of (1) placing films and X-ray dosimeters on a stair test block; (2) exposing; (3) washing and drying the exposed films, utilizing a nigrometer to measure blackness values of negative films, reading accumulated doses corresponding to the blackness values to obtain a group of blackness values, and then finding an accumulated variable H corresponding to a standard blackness; (4) transilluminating a testing block to be detected with certain thickness under different transillumination conditions, stopping the transillumination when the accumulated variable is H, and recording light exposure at the time; (5) repeating the step (4) for multiple times to obtain a plurality of groups of light exposure under different transillumination conditions; (6) obtaining the exposure curve according to the thickness, the blackness values and the transillumination conditions of the transilluminated testing block to be detected with the certain thickness. According to the method for preparing the exposure curve for radiographic inspection, based on a relative relation between the blackness and the light exposure, the exposure curve can be obtained by only developing the films once, so that a plurality of films can be saved, and time-saving and labor-saving operation can be realized.