Mg(92)Zn(6)Y(1.5)Zr(0.5) alloy was extruded at 300, 350, 400 degrees C. Then, the alloy was aged at 180 V. The microstructure and mechanical properties of the extruded alloy and aged alloy were investigated. The precipitation behavior of aging process was investigated. The increase of yield strength at room temperature and ultimate strength at elevated temperature after the aging process has been ascribed to the strengthening effect of these precipitates.