Abstract: The current application of industrial X-ray CT technology to observe the internal microstructure and mechanical properties of geotechnical soil has become a hot topic in engineering geology. However, the "large, heavy, dangerous, expensive" of the existing CT technology limits the field application capability, and the conventional geotechnical engineering survey method has the problem of losing or destroying the original geological information. This paper proposes the concept of in-situ CT technology and points out its key technologies in the application of geotechnical engineering. Based on the ultra-small cold cathode pulsed X-ray tube and imaging equipment, the in-situ CT experimental platform was built. The experimental results show that the method can realize in-situ digital sampling and CT rapid reconstruction. On this basis, the key points and key technologies of the follow-up research are clearly defined, including the new theory and new method of 2D/3D CT rapid reconstruction, and the analysis of the relationship between CT reconstructed image and geotechnical particle characteristics, and the local fine structure reconstruction algorithm, and the development of in-situ core 3D microstructure model. 3D printing technology will be combined to prepare the original position rock soil quasi-samples used to study the mechanical properties. A time-space four-dimensional geotechnical engineering measurement database will be established, and artificial intelligence algorithms were introduced to form a feedback evaluation system with learning and prediction. It is of great scientific significance to enrich existing geotechnical engineering survey methods and improve in-situ CT technology.