Casting method and device of magnesium alloy

The invention relates to a casting method and device of magnesium alloy, and is applicable to casting of complex thin-wall magnesium alloy castings at high technological quality. According to the method and the device, an overheated magnesium alloy melt in a liquid supply molten pool is filled into a casting mold cavity placed in a vacuum or protective atmosphere sealing housing through a thermal insulation casting pipe under atmosphere protection under the driving of a vacuum suction or quantitative pouring mechanism; when the liquid level of a casting mold riser reaches a required height, casting is stopped; the melt in a casting mold can be solidified under the vacuum or protective atmosphere of the sealing housing; the sealing housing can also be pressurized as required, so that the melt in the casting mold is solidified under a pressure environment which is equal to or higher than barometric pressure; thus the magnesium alloy casting which is compact in the interior and non-casting and causes technological defects due to mold filling is obtained.