The application of the magnesium alloy die casting and rolled magnesium alloy on strength parts is investigated by the mechanical properties which are tensile test, fracture toughness test and fatigue crack propagation test. Especially, the magnesium alloy made by the die casting is compared with the aluminum alloy which is used for the vehicles as the strength parts. In consequence, the magnesium alloy die casting need to surpass the 0.2% proof stress relative of the aluminum alloy. Moreover, the fracture toughness and fatigue crack propagation of magnesium alloy approximate to the aluminum alloy. The rolled magnesium alloy can sustain rather the bending moment than the tensile load. And the joint of rolled magnesium alloy that resist 100N・m on the proof stress of AZ31 and the pipe with 30mm in diameter and 2mm thick is proposed. The joint react to increase the diameter of magnesium alloy.
