Abstract: A combined forward mixing and backflow model has been organized to meet the nonideal flow in countercurrent liquid-liquid contactors.TWo effects have been considered in the model:1)the forward mixing by drop size distribution and 2)the backmixing of dro-plets.Experiments in a extraction column showed that the RTD curves In dispersed phase predicted by the model fitted experimental data vecy well.In mass transfer calculation,the numbers of transfer unit prcdicted by the model were in good agreen1ent with experimental data.