Abstract: Based on the principle of preparing semi-solid slurry by mechanical stirring, the technology of medium cooling and cooling stirring semi-solid was developed by passing the cooling medium into the stirring shaft to change the heat dissipation condition. The solidification temperature field and solidification microstructure of the aluminum alloy melt under the heat dissipation and stirring of different cooling media were numerically simulated and experimentally studied.The results show that stirring can convect heat transfer between melt and stirring shaft, so that the temperature field drops evenly to the subcooled temperature range, promotes nucleation, destroys the dendrite growth environment, and obtains nearly spherical structure.Superimposed medium cooling increases the heat dissipation of stirring shaft, forming a melt-stirring shaft-medium continuous heat exchange structure, greatly reducing the time of melt falling to the subcooling temperature range, faster to achieve bigger subcooling, further promoting nucleation, refining grains. At the same time, the stirring shaft can be rapidly reduced to room temperature under the condition of medium cooling after the pulping, and the stability of semi-solid slurry preparation can be ensured by the stability of the initial conditions of each pulping, which is very suitable for the fast rhythm mass production of rheological die casting.