<p>The effects of solute on the generalized stacking fault energy of basal plane, prismatic plane and pyramidal slip systems in Mg-X binary magnesium alloy have been systematically studied by using first-principles density functional theory (DFT). The addition of elements having low elastic modulus, larger original size and lower first ionization energy is considered to improve the plasticity of magnesium alloy. Starting from the formation process of dislocation, the synergistic effect and comprehensive effect of alloying elements on multiple slip systems are established. Based on the weight of the slip system, the stacking fault energy distribution diagram of GSFE weight model is established, and good consistency is obtained between the results of those of GSFE weight model and DFT. At the same time, the activation probability result show that &lt; a &gt; the activation probability of basal plane dislocations is more than twice that of pyramidal plane dislocations. It accords with the preferential activation of basal slip system at room temperature &lt; a &gt; . The plasticity of magnesium alloy can be improved remarkably by activating pyramidal type II &lt; c + a &gt; dislocations. The ductility of alloys can be assessed qualitatively in terms of pyramidal slip systems.</p> Graphical Abstract <p></p>