The invention discloses an X-ray layered photography detection method and a system; the system comprises an X-ray tube, a plane X-ray detector, a stage and a control and calculation device; and the stage is arranged between the X-ray tube and the X-ray plane detector; and the calculation device controls the translation of the stage in the X-axis direction and the Y-axis direction and the rotationof the X-ray plane detector, and processes X-ray images obtained by the X-ray plane detector. The detection method comprises the following steps that: an object to be detected is detected progressively row by row, rotary translation follow-up scanning is carried out every row, and the multi-angle X-ray image of the object to be detected is obtained; the images of the cross section of a ZX center are combined and overlaid to reconstruct the stub of the object to be detected; the outline of the cross section of the ZX center of the object to be detected is obtained by fitting; and the defects of slight open joint, dry joint and other welding points can be judged according to the detection level sub length of the object to be detected and set judging criteria.