Abstract: This paper points out that expanding clay minerals can absorb uranium and gives a list of clay minerals with rich or poor uranium occuring in structural fracture zone.And characteristics of the clay minerals are described by means of electron microscope and various analyses such as differential thermal analysis, infrared absorbed spectral analysis, x-ray diffraction and chemical analysis.The conclusion is that the uranium content in the regular interstratified chlorite-montmorillonite mineral is the highest, even up to 0.246%.The main mineral,montmorillonite, plays an important role in absorbing uranium.The experiment data indicate that under the same conditions Na-montmorillonite absorbs more uranium than Ca-montmorillonitc. The mechanism of uranium absorption is, described as follows. The montmorillon-ites are characterized by ion-change ability and absorbing water, which can offer fasorable condition for uranuly ( UO ) moving into structural layers.In addition, because of the fine grain of the montmorillonites and their large sarface area they can absorb more uranium .Furthcrmore, the environment in which monimerillonites occur is favorable for uranium accumulation.