Abstract: The down-press stirring tank with multi-mixer (DPSTMM), a new type of mixing tank, was developed, which consists of several mixing chambers in a vertical series. The fluid flows down from chamber to chamber in 0. 65 liter and 65 liter DPSTMM. The number of mixing time Nθm was obtained, the energy consumption per unit mass was measured and the axial mixing coefficients were determined by computer from the response curve of tracer concentration. Experiments were carried out in 65 L DPSTMM, with kerosene/oc-tanol (10 : 1,V/V) as continuous phase and water as dispersed phase. HAc transfers from water to kerosene/octanol. The overall coefficient of mass transfer, Koda, in different mixing chambers was calculated by means of cascade extraction principles to analyse the overall efficiency of scaled - up DPSTMM. The experimental results showed that DPSTMM had much better performance than continuous stirring reactor tank (CSRT) in hydrodynamics and mass transfer.