Abstract:In this paper, the Cloud occasion ore of 721 uranium mines was selected to study the characteristics of thorium leaching in the process of uranium mines bacteria tank leaching .The results indicated that hydrogeochemical conditions(pH and Eh) have little effect on the leaching of thorium in the process of column leaching, over time, pH values changed between 1.73 to1.36, Eh values changed between 169mV to 592mV, but the amount of Th leaching stable at 2.2 mg / L to 2.5 mg / L .At the same time,during the experiment, the leaching rate of uranium is 80.03%, the leaching rate of Th is just 14.1%,mainly because of the different chemical properties between U and Th.Th is difficult to be dissolved,migration and transformation because Th is present in the ore with the stability form 4 price.U has multiple valence states,it is easy to transport and transformation in the environment,because U is present in the ore with the lively form 6 price.