<p>Carbonaceous debris (CD) is widely disseminated within sandstones in the Shuanglong uranium deposit, southern Ordos Basin, and is the dominant enrichment agent for uranium precipitation. The occurrence and chemical composition of uranium minerals within CD were investigated by using scanning electron microscope and electron microprobe analyses. The results show that uranium minerals mostly occur in cell pores in the forms of fructus aurantia and concentric band structure. Pitchblende and coffinite are the main uranium minerals, and the former is dominant. According to the crystal morphology and composition of trace elements of uranium minerals, uranium precipitation on the pores is grouped into two periods, orderly I, II. Moreover, the I period is further divided into two sub-period, orderly I₁, I₂. Moreover, askew sphere uranium minerals could indicate fluid migration. Under certain geological environment condition, uranium is unevenly adsorbed on the surface of the pore by the Van der Waals (i.e., I₁ period), and then is precipitated towards to the center of the pore until the whole pore is filled up with uranium minerals by complicated process such as microorganism activities (i. e., I₂, II period). It will provide some guidance for studying the metallogenic environment and genesis of sandstone-type uranium deposit.</p>