Abstract: A total of 610 data are used to testify the realibility of U(Ⅳ) distribution models which were established by different researchers from United States, India and Japan with the Matlab software. The results show that the model established by United States researcher is the best one among the three models, but the relative deviation is still more than 20%, and the model can not be used to calculate the U(Ⅳ) distribution. Thus, the model established by United States researcher is chose to be modified, the modified model is D(U(Ⅳ))=K*(U(Ⅳ))c²(fTBP), and K^*(U(Ⅳ))=(1.4/(30×c(U(Ⅳ)）＋1))×K*(U(Ⅵ)）×(0.0541＋0.000658×c²(NO^-₃)). The modified model can be used in the following equilibrium concentration ranges for the aqueous phase: HNO 3 0.4-4.0mol/L, U(Ⅳ) 5-50g/L, U(Ⅵ) 15-150g/L, Pu(Ⅲ) 0.4-36.3g/L, hydrazine 7×10^-4-2mol/L. The relative deviation of the modified model is less than ±15%.