The effects of extruding temperatures on the microstructures and mechanical properties of the Mg-2.0Zn-0.3Zr-0.9Y magnesium alloy were investigated. The results show that the grain size of Mg-2.0Zn-0.3Zr-0.9Y alloy is significantly refined by decreasing the extruding temperature. Meanwhile the tensile strength and the yield strength are greatly enhanced, but the elongation is increased little. With the decrease of extruding temperature, the intensity of {102} texture is enhanced, while that of the {0002} basal ring type texture is decreased. The mechanical properties of the alloy are not only related with the average grain size, but also with the texture. Mg-2.0Zn-0.3Zr-0.9Y magnesium alloy extruded at 330 °C possesses a fine grain size of 1.76 μm on average and good mechanical properties including the elongation of 21.92%, the yield strength of 309 MPa and the tensile strength of 323 MPa.