The effects of minor Zn(0.2 at％,0.4 at％,0.6 at％)on the microstructures and mechanical properties of Mg-1.4Gd-1.2Y-0.15Zr(at％)alloys were systematically explored.Results reveal that increasing Zn content leads to the increase of the intergranular phases and the change of their composition from Mg24(Gd,Y)5 phase and(Mg,Zn)3(Gd,Y)phase to 18R-LPSO phase and(Mg,Zn)3(Gd,Y)phase.Mg24(Gd,Y)5 phase is body-centered cubic structure and shares the same lattice constant with Mg24Y5 while(Mg,Zn)3(Gd,Y)phase is face-centered cubic structure with lattice constant of 0.72 nm,slightly lower than Mg3Gd.18R-LPSO structure is identified to be monoclinic with c-axis not strictly vertical to the bottom surface but 93.5.The growth patts of intergranular phases change from the divorced growth to coupled growth as compositions change.Moreover,the mechanical performance improves with Zn rising,ascribed to the decrease of brittle phases at grain boundaries and the increase of LPSO structure phases.