This work focused on the grain reﬁnement and investigation its effect on the microstructural evolution and mechanical properties. The magnesium alloy AZ31 sheet was processed by repeated cold rolling and recrystallized annealing. From the experimental works, the ﬁne and equiaxed grains with less than 5 μm were achieved. It was found that for annealing at temperatures in the range of 523–673K, sample was fully recrystallized less than 30 minutes and after that the growth of the recrystallized grains is slight. Finally, the tensile tests were carried out to analyze the changes in the strength and fracture elongation.