Geological,geophysical and hydrogeological means were applied to the study of radioactive anomalies in eastern Qaidam basin.Based on analyzing the depositional environment,hydrogeological environment and material composition of sand bodies in the anomalous area,this paper studied in detail the genesis of radioactive anomalies in Quaternary sediments(Q_3-4).Some conclusions have been reached: 1.The anomalies result from the leaching of Quaternary detrital minerals;2.The anomalies are spatially controlled by the mud-platform facies of Quaternary(Q_3-4) alluvial fan margin and the oxidation-reduction interface of phreatic water.It is thought that the anomalies are valuable in the study of metallogenic process,but have little significance in guiding ore prospecting work at depth.