The invention relates to an alloy powder cored wire, particularly to a rare earth magnesium alloy cored wire containing multiple elements. The cored wire is characterized in that the outer layer is an ordinary steel belt of which the thickness is 0.3 mm to 0.5 mm; the core part is rare earth magnesium alloy powder; a powder layer with a thermal insulation function is positioned between the outer layer and the core part; the alloy powder comprises the following element components by mass percent: 10% to 20% of Mg, 0.5% to 2.5% of Ca, 1.0% to 2.5% of Al, 25% to 35% of Si, 1% to 2.5% of Ti, 0.5% to 3.5% of Ba, 2.5% to 5.0% of Mn, 0.5% to 1.0% of Nb, 0.5% to 1.0% of V, 1.0% to 5.0% of rare earth elements, 0.1% or fewer of P and 0.1% or fewer of S, and the balance being of Fe. According to the cored wire, the alloy powder is added into microalloyed steel in a cored wire manner, so that the magnesium treatment process is stable, relatively high absorptivity can be acquired, and current problems are solved relatively well.