Abstract：The authors studied the mode of occurrence, main accompanying elements and precipitation mechanism of sandstone-type minerals in the Diantou area of the southeastern Ordos basin by using the electron microprobe and microprobe. The dominant uranium mineral in the study area is pitchblende, which occurs as microdisseminations filling in pores and cements of sandstone. The elements associated intimately with uranium are Fe, Se, Pb, Si, Ti, Cr and S and the mineral assemblage of uranium includes pyrite, galena, brannerite and its closely related selenium mineralization. The main uranium-bearing horizon contains rich organic matter and pyrite, intercalated with lenticular and banded coal seams. It contains abundant reducing material, which is favorable for uranium reduction and concentration. Therefore, the authors think that the reducing barrier and adsorption barrier are the main factors responsible for uranium deposition in the study area.