Abstract: Dynamic recrystallization behaviours of Al-Mg alloys during hot deformation are investigated by means of polarized light microscopy and electron microscopy.The results show that dynamic recrystallization taks place in a certain range of parameter Z in Al-2Mg and Al-6Mg alloys and dynamic recrystallization behaviour of Al-9Mg alloy is similar to those materials having a lower stacking fault energy. Dynamic recrystallization is accelerated by increasing Mg content, which results from that Mg atmospheres impede cross slip of dislocation, so that dynamic recovery is difficult to cccur.