Abstract: The Mg-5Y-2Nd-1Gd-0.5Zr (wt%, WE53) magnesium alloy is prepared by gravity casting in order to improve mechanical properties of WE series biodegradable magnesium alloys. Solution treatment (T4), solution + aging treatment (T6) and extrusion are conducted on the as-cast alloy. Microstructure of the alloy is observed by optical microscopy and scanning electron microscopy. And mechanical properties at room temperature are measured by tensile test machine and microhardness tester. The results show that the yield strength and elongation of the as-cast alloy are 130 MPa and 10.2%, respectively. The strength and hardness of the alloy are apparently enhanced but the elongation is decreased by T6 treatment. Extrusion can improve the strength and hardness of the alloy significantly, and the elongation is close to that of the as-cast alloy. The mechanical properties of the WE53 magnesium alloy can be improved significantly by proper heat treatment and extrusion processes.