Mg-10Gd-3Y-1.2Zn-0.5Zr alloy was prepared by adding 1.2wt%Zn in Mg-10Gd-3Y-0.5Zr alloy. The microstructures and mechanical properties as well as fracture behaviors of the alloys at the different conditions were studied by using optical microscopy, scanning electron microscopy and tensile testing machine.The results indciated that the cast case showed a poor plasticity, however, T4 alloys had a good plasticity, and the plasticity of T6 state was between the cast and T4 conditions. All the specimens mainly attributed to brittle cleavage fracture, and the bonding strength at interface of grain boundary and lamellar phase was stronger than the compound interface.Compare to the T6 mechanical properties at three different temperatures, it was found that improving solution temperature could improve the alloy strength, however, the elongation rate reduced slightly. The Zn can promote the growth of lamellar phase, however, only a limited role for plastic characteristics of the matrix could be observed.