Abstract: By comparing and analyzing lots of reported data of technetium with the computing results, a modification function P(c⁰(U)，t) was introduced to the existing distribution coefficient model of technetium, and a new mathematical model for simulating technetium extraction behavior in the system of UO₂(NO₃)₂-TcO₄^--HNO₃-H₂O/TBP kerosene was established, as well as a computer program. The reliability of the program was verified by 179 sets of distribution coefficient data, and the results were found to agree well with experimental data. By comparing the reported data of technetium with the computing results, an evaluation was made to test the performance of the revised model. It turned out that the calculation results of the new model were more reliable than that of the one reported previously. The revised model and program can be the foundation to simulating technetium extraction behavior in the system of UO₂(NO₃)₂-TcO₄^--HNO₃-H₂O/TBP kerosene with the temperature scope from 10 to 60 ℃, U concentration from 0 to 280 g/L, and nitric acid concentration from 0.1 to 5 mol/L.