Abstract: A computer program was developed to simulate technetium scrubbing section (TcS) in Purex process based on the theory of cascade extraction. The program can simulate the steady-state behavior of HNO₃, U, Pu and Tc in TcS. The reliability of the program was verified by cascade extraction experiment, the relative error between calculation value and experiment value was 10% more or less except few spots. The technical parameters of TcS were analyzed by this program. It is found that the decontamination factor (DF(Tc/U)) in TcS is remarkably affected by the overall consumption (the product of molarity and volume flux) of HNO₃, DF(Tc/U) is increase with the increase of the over consumption of HNO₃. Changing the combination of HNO₃ concentration and flow ratio can not remarkably improve the DF(Tc/U) in TcS if the overall consumption of HNO₃ is fixed. An inflection point exists when DF(Tc/U) changed with HNO₃ contraction, the optimum combination of HNO₃ concentration and flow ratio is given by this point.