The Mg-9Al-5Sn-xSb (x =0.0,0.3,0.6,1.0,1.5 wt％) alloys were prepared by a simple alloying process followed by hot extrusion with an extrusion ratio of 28.2.The effects of Sb additions on the microstructure and mechanical properties of the Mg-9Al-5Sn alloys were investigated by optical microscopy,X-ray diffraction,transmission electron microscopy,scanning electron microscopy equipped with an energy-dispersive X-ray spectrometer.The results indicated that the phases α-Mg matrix,Mg2Sn,Mg3Sb2 and Mg17Al12 exist in the as-cast Sb-containing alloys.Sb addition results in the precipitation of Mg3Sb2.The dendritic size of these alloys decreases with the addition of Sb.Both their ultimate tensile strength and yield strength of extruded alloys increase,and their elongation decreases gradually with increasing the content of Sb.The better mechanical properties of the as-extruded alloys were achieved due to the refined grains and the formation of dispersive second phases Mg3Sb2.