Abstract: Microstructure and mechanical properties of Mg-3Zn-xY(x=1.5,3,6) alloys were investigated.Results indicate that the amount of particles in the matrix and at grain boundaries increase with increasing yttrium content.The type of the second phase in the alloy depend upon the Zn/Y ratio,as the Y content increases,the second phase is transformed from I-phase + W-phase to W-phase + H-phase ,and to H-phase.The shape of second phases at the grain boundaries transformed from short rodlikes to reticular particles.With the Y content increasing,the alloy’s tensile strength,hardness and impact toughness increases,but the plasticity decreases.The mechanical properties descended when the Y content is higher than 6wt%.