Abstract: The extrusion tests of Mg-9Gd-4Y-2Zn-0.5Zr alloy with different extrusion ratios were carried out.The effects of different extrusion ratio on the microstructure and mechanical properties of the alloy were studied by OM, SEM and tensile tests.The results show that the microstructure of the homogenized alloy is mainly composed of α-Mg matrix, layered LPSO phase and a small amount of lumpy LPSO phase.With the increase of extrusion ratio, the recrystallization degree of the alloy becomes higher and the lamellar LPSO phase decreases gradually. Compared with those of the homogenized test alloy, the strength and elongation of the extruded alloy are improved obviously.With the increase of extrusion ratio, the strength of the alloy increases slightly and the elongation increases obviously. The tensile strength, yield strength and elongation of Mg-9Gd-4Y-2Zn-0.5Z alloy with extrusion ratio of 42 reach the maximum values, which are 407, 332 MPa and 12.2%respectively.