Abstract: The as-cast Mg-9Gd alloy was extruded, and then was hot treated, the microstructure and mechanical properties of the Mg-9Gd alloy after different treatments were studied. The results show that the extruded alloy contained amounts of refine equiaxed grains and a small number of intermediate phases, and the later was broken to massive block particles along the stress direction distribution in belt. Comparing with the as-cast alloy, the tensile strength (σb) and the yield strength (σ0.2) of the extruded alloy increased by 89.8% and 44.1% , and the elongation reached to 19.5%. The σb and the σ0.2 decreased after the extruded alloy was treated by 520 ℃×2 h+200 ℃×8 h, and the σb, σ0.2 were 231.4, 129.3 MPa, and δ was 15.2%. The aging treatment of 200 ℃×14 h obviously enhanced the strength, σb and σ0.2 up to 254.2 MPa and 180.3 MPa, but the plasticity decreased further, and δ was 10.5%.