Abstract: The frequent occurrence of terrorist incidents has seriously affected the security and order of the international community, bringing unprecedented challenges to the safety of passenger and freight transportation. Effectively combating terrorist activities and ensuring personal and property safety are important demands in the field of public security both domestically and globally. Therefore, how to enhance security inspection capabilities through high-tech means has become an important issue and research hotspot of concern. X-ray diffraction (XRD) technology can identify prohibited substances at the molecular level, with high discrimination, and has broad application prospects in the field of safety inspection. Starting from the basic theory of diffraction, this article briefly describes the current research progress in the structure and recognition algorithms of XRD systems, as well as the advantages of XRD technology. An XRD system was built to verify its effectiveness. Finally, the development direction of XRD was prospected, with the aim of further promoting this technology to play a more important role in the field of public safety.