Magnesium alloy with high mechanical properties and preparation method of magnesium alloy

The invention provides a magnesium alloy with high mechanical properties and a preparation method of the magnesium alloy. An as-cast microstructure of an Mg-Al magnesium alloy comprises two phases as follows: an alpha-sosoloid serving as a matrix phase and a beta-Mg17Al12 phase serving as a strengthening phase. According to the magnesium alloy with high mechanical properties and the preparation method of the magnesium alloy, the adding quantity of Ga elements is controlled in a range of 1.6%-2.9% by weight, the problem that the mechanical properties including strength and plasticity of the alloy cannot be up to a higher value due to the smaller adding quantity of Ga elements can be solved, and the problem that the strength and the plasticity of the alloy are reduced due to the fact that the adding quantity is overlarge, the beta phase is fused, a new phase Ga2Mg forms and a three-phase eutectic comprising the alpha phase, the beta phase and Ga2Mg is formed can be solved.