The lead leaf of the x ray collimator plays a shielding role in the beam limiter and controls the dose of X-ray beam. At present, the structure of the lead leaf of the beam limiter mainly consists of two groups of single-layer and two groups of multi-layer. In order to shield stray X-ray, it is necessary to shield the shell or interior of the beam limiter with more lead plates. The multi-layer structure of the lead leaf of the beam limiter can meet the standard requirements of X-ray leakage. However, the stray scattering rays radiated through the beam limiter window can not be shielded, which directly affects the quality of X-ray images, especially when applied in digital X-ray diagnostic equipment.