The microstructure, mechanical and anticorrosion properties of Mg-0.5Zr-1.8Zn-xGd (x=0, 0.5, 1.0, 1.5, 2.0, 2.5, wt%) alloys were investigated after a solution treatment at 470 ℃ for 10 h. Results indicate that the grain size of the alloy decreases with increasing the Gd content in the range of 0wt%~2.5wt%. When the Gd content is less than 1.5wt%, the alloy elements are more completely dissolved into the alloy matrix, and the second phase is mainly composed of nanoscale (Mg, Zn)₃Gd precipitated particle. At the range of 1.5wt%~2.5wt%, the insoluble micron-scale (Mg, Zn)₃Gd phase emerges in the alloy, and the number and size of the (Mg, Zn)₃Gd phase increase with the Gd content. The Mg-0.5Zr-1.8Zn-1.5Gd alloy shows excellent mechanical properties and anticorrosive ability, which can be attributed to a more homogeneous microstructure and the presence of nanometric secondary phase particles. In the 120 h immersion experiment, the average corrosion rate of the Mg-0.5Zr-1.8Zn-1.5Gd alloy deceases at first, then increases, and then decreases slowly. At last, with the increase of immersion time, it eventually becomes stable.