In the process of aluminum alloy die-casting, the time for liquid metal to fill the mold cavity under high pressure and high speed is very short, generally only a fraction of a second. The initial stage is complete injection, and then in a short time, on the one hand, it fills all parts of the cavity, on the other hand, it changes in a very complex way until it fills the cavity. Correctly understanding the flow state and change of molten metal, mastering the law of metal filling shape, and making full use of this characteristic of molten metal are the decisive factors for reasonably designing the gating system and then making good die castings