Abstract: Friction stir welding was adopted to weld AZ80 magnesium alloy, the effects of welding rates on friction stir welding joint shaping and microstructure were studied under the condition of other parameters unchanging．The results show that the good surface quality and compact weld seam were obtained when the rotation rate was 1 000 r·min-1 and the welding rate was 150 mm·min-1. The dynamic recrystallization grains in the medium of advancing side of nugget zone decreased with the increase of welding rate, and the effect of welding rate on microstructure of thermo-chemical affected zone and heat affected zone was no difference.