The flow field of liquid phase (water) of agitated extraction columns is simulated with the help of computational fluid dynamics (CFD). Four kinds of Reynolds-averaged turbulence models, i.e. the standard k-epsilon model, the RNG (renormalization group) k-epsilon model, the realizable k-epsilon model and the Reynolds stress model, are compared in detail in order to judge which is the best model in terms of the accuracy, less CPU time and memory required. The performance of the realizable k-epsilon model is obviously improved by reducing the model constant from c(2) = 1.90 to c(2) = 1.61. It is concluded that the improved realizable k-e model is the optimal model.