The low-density magnesium (Mg) alloys are attractive for the application in aerospace, transportation and other weight-saving-required fields. It is noteworthy that the solid solution of alloying elements in the α-Mg phase can have multi-effects on the properties of Mg alloys, e.g, solid solution strengthening, solid solution corrosion-resistance-enhancing, etc. And it is also notably the functional properties, e.g. damping capacities, magnetic shielding properties can also be tailored by controlling the solution in the matrix. It is promising that by selected proper multi-alloying-elements (with optimal ratio) solid solution in the α-Mg phase, the comprehensive properties of Mg alloys can be synergy improved. In this work, the solid solution behavior of Mg alloys and the followed solid solution property-enhancing effects were studied. Three types solution behavior in the ternary magnesium alloy systems were proposed and the application for the materials design for specified functions were proposed.