The invention provides a magnesium alloy, which comprises the following components in percentage by weight: 0.5-1.5% of calcium, 0.5-2.5% of zinc, and the balance of magnesium, wherein the sum of weight percentages is 100%. The invention also provides a melting process of the magnesium alloy, which comprises the following steps: (1) slicing magnesium ingots and removing impurities, and weighing zinc and calcium for standby; (2) preheating a crucible and a die; (3) putting the magnesium slices into the crucible, putting the crucible in a furnace, and after an operation of vacuumizing is completed, feeding mixed gas into the furnace; (4) heating the furnace until the magnesium slices are completely molten, and heating and stirring the obtained product; (5) wrapping metal calcium with an aluminum foil, adding the obtained object in the bottom of molten magnesium, then adding zinc slices, carrying out stirring and slag removal on the obtained mixture, and after the obtained product is heated, carrying out heat preservation on the obtained product; and (6) cooling molten liquid, carrying out heat preservation on the molten liquid, opening the furnace, taking the die, pouring the molten liquid into the die, and waiting. The invention also provides a heat treatment process of the magnesium alloy, which comprises the following steps of (1) homogenized annealing; and (2) solid solution treatment. The magnesium alloy disclosed by the invention has the advantages that the mechanical properties of the alloy are improved, the casting performance is improved, and the creep resistance of the alloy is increased.