Abstract: The extraction of Ce(Ⅲ) nitrate was investigated by using N,N′-dimethyl-N,N′-dioctyl-diglycolamide (DMDODGA) as extractant with 40% octanol/kerosene as diluent. DMDODGA shows good extraction ability for Ce(Ⅲ), but the trends are quite different depending on the concentrations of nitric acid in aqueous phase, and the peak value of distribution ratio varying with the concentration of nitric acid and moves towards low acidity with the extractant concentration increasing. The slope analysis method was used to obtain the stoichiometric ratio of the extracted complexes. The results show that 1∶3 complexe of Ce(Ⅲ) to DMDODGA is formed in DMDODGA-octanol/kerosene system. The expected charged 1∶3 complex of Ce(Ⅲ) is formed in the 40% octanol/kerosene, and the complex is a neutral complex with three DMDODGA molecules directly bonding to Ce(Ⅲ) and three nitrate anions. In addition, the stronger interaction between the C＝O groups of DMDODGA and Ce(Ⅲ) in the 40% octanol/kerosene system is confirmed by IR spectroscopy. The results of the back extraction show that the stripping of Ce(Ⅲ) is difficult from organic phase using three common stripping agents, due to a strong interaction between Ce(Ⅲ) and DMDODGA.