The invention discloses a magnesium alloy ingot casting production line and a production method thereof. The magnesium alloy ingot casting production line divides an insulation furnace into three cavities of a transfer cavity, a standing cavity and a casting cavity, so that molten magnesium is subjected to multiple times of standing and layering in the insulation furnace, and a cleanest middle layer is guaranteed in the casting cavity for casting a magnesium ingot; a liquid level balance controller is arranged in the standing cavity; the feeding and the stop of feeding of the molten magnesium are controlled through a control system; a surface treatment device is mounted on a continuous casting machine; and a PLC controls a cylinder to automatically spray the surface of the magnesium ingot. The magnesium alloy ingot casting production line is simple in structure and convenient to use, can improve the purity of the magnesium ingot, meanwhile, realizes automatic casting and spraying, reduces the manual operation intensity, and improves the product quality.