Abstract: To explore the migration behavior of Pu in high salinity groundwater from granite area in Northwest of Lop Nor region, the distribution and chemical species of Pu(Ⅳ) were studied after Pu(Ⅳ) added into the groundwater and aged for one year. The results show that the distribution and chemical species of Pu reach the equilibrium after one year’s aging in the groundwater. 90% of spiked Pu is transformed into colloidal species in short-term (30 d) and is adsorbed on the container wall. For the minority of Pu in water phase, most of it is dissolved species (or particles smaller than 3 nm) while the left is colloidal species (particles larger than 450 nm) in solution. Pu is desorbed from the wall of container, which can be attributed to the increase of the dissolved oxygen and/or the pH when the samples are shaked in the air. The chemical species of colloid-associated Pu (pseudo-colloid) is checked with sequential extraction method as carbonates (57.3%), organic matter (21.7%), Fe-Mn oxides (11.2%), residual (5.1%) and exchangeable (4.7%), while the oxidation state of dissolved Pu comes as Pu(Ⅳ) (71%), Pu(Ⅴ) (24%) and Pu(Ⅵ) (5%). The results of present work imply that a majority of Pu(Ⅳ) can be associated with colloid in high salinity groundwater (contained a mass of colloid and flowed very slowly) from granite area, and thus adsorbed on rock surface which can not transport through granite fracture. While the rest part, mainly dissolved in groundwater, may transport along with the water’s flow. Pu on granite surface can be desorbed with the increase of the dissolved oxygen and/or the pH of the groundwater, and thus the migration of Pu will be enhanced.