Abstract: An improved box mixing/clarifying tank was proposed to solve the problem of mixing/clarifying tank. The flow characteristic was simulated and studied by ANSYS/FLUENT in the improved new type mixing/clarifying tank. When the speeds of oil and water are 0.22 and 0.11 m/s, respectively, the rotation speeds of mixing room and clarifying room are 800 and 20 r/min, respectively, compared with the traditional extraction tank, the mixed zone is thinner near the blades in the new mixing/clarifying tank, and the two-phase separation effect is better under stirring. The flow field is vortex flow near the blades in the mixing room, and this is agreement with the flow characteristic of rushton turbine.