Abstract: The present disclosure discloses a Mg—Al based magnesium alloy, and a preparation method of a tube and an application of the same, and belongs to the technical field of alloy materials. The magnesium alloy includes, by weight percentage, 7.0-8.6% Al, 0.8-2.0% RE, 0.2-0.8% Mn, and a balance of Mg, and the magnesium alloy has an elongation of 15-22%. The preparation method of a tube of the Mg—Al based magnesium alloy includes: mixing and smelting an Al source, a RE source, a Mn source, and a Mg source to give a liquid mixed metal; casting the liquid mixed metal into a bar through semi-continuous casting; performing homogenization heat treatment on the bar at 360-400° C. for 6-10 h; and performing extrusion-forming on the heat-treated bar to obtain a magnesium alloy tube. The Mg—Al based magnesium alloy of the present disclosure has high elongation, and the elongation of the tube formed using the same can reach 15-22%, so that it can withstand large plastic deformation.