Abstract: The effects of proton and ion irradiations on tensile property, surface hardness and deformation-fracture behavior of Mg-Zn-Y-Zr alloy are studied in this paper. The results show that there is little difference in the tensile properties and the tensile fracture features after the proton and nitrogen ion irradiations, with the energy of 170 keV and the fluence of 5×10¹⁵ /cm², 1×10¹⁶ /cm², 2×10¹⁶ /cm² and 1×10¹⁷/cm², respectively. This might be due to the shallow depth of the proton or ion particles injected into the alloy. It is also shown that the nano-hardness of ion irradiated surface is increased as the irradiation fluence increases, indicating the favorable hardening effect of ion irradiation on the Mg-Zn-Y-Zr alloy. On the contrary, no significant hardening effect on the investigated alloy was observed after the proton irradiation.