Abstract: The distribution ratios of low concentration UO 2(NO 3) 2(initial mass concentration lower than 10 g/L) and HNO 3(initial concentration 0～2 mol/L) between dilute TBP/kerosene(lower than 10%) and aqueous solution in the presence of Al(NO 3) 3 are determined. Based on these data, the empirical functions of extraction equilibrium concentration quotients K (U(Ⅵ)) and K (H +) are founded by non linear least square fitting method. According to these functions, D (U(Ⅵ)) and D (H +) can be calculated out and they are in good agreement with observed values. The mean error of calculated D (U(Ⅵ)) is about 10%; and the mean error of calculated D (H +) is less than 5%.