Abstract: Gadolinium has been proposed for use as neutron poison for the control of criticality during the spent nuclear fuel dissolution, feed preparation, and solvent extraction.The distribution ratio of gadolinium (Dad) in system TBP-nitrate, concentration profiles of Gd in countercurrent extraction process with TBP and solubility of gadolinium nitrate in aqueous solution are presented. The effects of concentration of nitric acid, sodium nitrate, uranyl nitrate and gadolinium nitrate, temperature, and irradiation of TBP-kerosene on Dad, are investigated.A maximum and a minimum on Dad vs. nitric acid concentration curves at about 3 mol/1 and 7 mol/1 nitric acid are observed respectively. Dad increases with the increase of concentration of sodium nitrate in aqueous phase. Maximum and minimum of Dad are not found in sodium nitrate solution. Uranium concentration in equilibrated organic phase influences Dad significantly. The change of Dad is not appreciable when gadolinium concentration in aqueous phase increases to 13 g/1.No difference can be seen between Dad with solvent irradiated by 80Co to a level of 3.6×105 Gy and DGd with solvent not irradiated.Cascade countercurrent extraction tests are carried but and decontamination factors from Gd of 104-105 are obtained.The effects of some factors such as concentration of nitric acid and uranium,and temperature on the solubility of gadolinium nitrate in aqueous solution are investigated. The results show that the value of solubility of gadolinium nitrate in aqueous solution decreases with the increase of concentration of nitric acid and uranyl nitrate.