In the past two decades, the visualization experiment technology for transparent geotechnical materials has developed into a method of observing deformation, fluid flow and other internal changes of rock and soil. This paper reviews the emergence and development of transparent rock-soil experiment technology, the preparation for different kinds of transparent geotechnical materials, the experiment equipment, the optical observation method, and the engineering application of this technology. In the traditional physical similarity experiment, the deformation law and the diffusion process of fluid flow cannot be observed directly because of the opaque medium. Therefore, a large number of scholars combined with optical measurement means and digital image processing technology to study the deformation and fluid flow in the rock and soil. Compared with the physical similarity experiment, this technique not only can realize the visual observation of geotechnical engineering change process, but also has the advantages of involvement of simple device, easy operation and low cost. It is also pointed out that it is in urgent need of establishing technical standards for the preparation of transparent rock-soil samples and the determination of engineering property indexes. [ABSTRACT FROM AUTHOR]