Abstract: A water model was builted by employing 1:4 ratio to simulate 210 t multi-function RH devices. The flow pattern of molten steel and the influence of argon blowing quantity,snorkel insertion depth and the number of argon blowing holes on the flow field of molten steel and mixing time were investigated by the water model. The results show that a main backflow and lots of small backflows exist in the steel ladle,and the decline fluid flow from the down tube forms a liquid-liquid two-phase flow,which plays a critical role in mixing and transforming in the steel ladle. The conclusion about ‘short flow’ that exists between the down tube and the offtake pipe in early studies is denied by the flow pattern in the RH steel ladle in this paper. The argon blowing quantity,snorkel insertion depth and the numbers of the upper and lower argon blowing holes influence the mixing time of molten steel obviously,but the argon blowing quantity and the number of lower argon blowing holes are stronger.