Abstract: A computer program named MIXEX2 is developed based on the steady state approach model in order to simulate the performance of multi stages contactor. Experiments are carried out to estimate the efficiency in the partition of U/Pu with N,N dimethylhydroxylamine (DMHAN) as reductant and the reliability of MIXEX2. The results show that Pu and U can be separated effectively under the designed condition with separation factors of SF Pu/U and SF U/Pu both over 10 4. Meanwhile, the calculated concentration profiles of HNO 3, U and Pu are in good agreement with their experimental concentration profiles. Therefore it can be said safely that the program can predict the working performance of extraction contactor successfully.