Cast magnesium alloy refining device and refining method based on device

The invention discloses a cast magnesium alloy refining device and a refining method based on the device, and belongs to the field of metallurgy. The method includes the steps that the gas outlet pressure and gas flow of a gas container are set through a gas pressure adjusting device, gas is fed into a magnesium alloy melt container containing magnesium alloy melt, and the liquid level of the magnesium alloy melt is made to roll stably; and a refining agent is scattered on the rolling liquid level to complete refining. The method further includes the steps of opening a switch valve of the gas container before refining is started and closing the switch valve of the gas container after refining is completed. Compared with a traditional manual stirring refining method, the labor intensity of operators can be greatly reduced in the magnesium alloy refining process, and meanwhile the uniformity and stability in the refining process are improved. In addition, the device and method can be applied to large-tonnage magnesium alloy melt refining, and the problem that refining is hard to achieve in the large-tonnage magnesium alloy melt treatment process is solved.