The effect of rotational speed and post annealing on the microstructural homogeneity of friction stir processed 5083 aluminum alloy was evaluated. In the FSP-affected zone (FAZ) grain size increased with the rotational speed from 450 to 850 rpm. While the rotational speed further arising up to 1650 rpm, the grain size was almost invariant. With a rotational speed of 450 rpm grains grew up to extremely large size and occupied nearly half area in FAZ. Before 850 rpm increasing rotational speed could reduce extreme grain growth in post annealing. However, the post annealed microstructure of the specimens 850-1650 rpm was similar, in which the survived initial fine grains occupied about 60% area of FAZ. The effect of stored energy induced by the different rotational speeds on the microstructural homogeneity of post annealed FSPed specimens was also discussed in this study.