Abstract: The effect of rotary motion on the fluid flow and the mixing characteristics in a tundish for electromagnetic purification were studied by a physical modeling method. The visualization of flow pattern and the measurement of residence time distribution (RTD) were performed under different rotation speeds and geometric configurations. The result shows that rotational flow in the cylindrical chamber can effectively decrease the dead volume and increase the plug volume. Meanwhile, the mean residence time is prolonged thereby promoting the removal of inclusions. The flow characteristics do not become better with the rise of rotation speed, but there exists an optimum value.