Abstract: Using keronese as diluent, U(Ⅵ) and Th(Ⅳ) can be extracted effectively by N,N di(1 methylheptyl)acetamide(DMHAA) from nitric acid solutions. The effects of the concentration of the nitric acid, salting out agents in aqueous phase and the extractant in organic phase on distribution ratios are examined. Under the same conditions, the distribution ratio of U(Ⅵ) is higher than that of Th(Ⅳ). The extraction mechanism are discussed.