Abstract: 2 mm thick 5083 aluminum alloy plates were butt welded by friction stir welding, and defect-free welded joints were obtained. The effect of welding thermal cycle on the grain structure of the welded joints was studied by optical microscopy and electron backscatter diffraction. The obtained results showed that with the increasing of the tool rotation speed, the strain rate enhanced, and the initial recrystallized grains which caused by dynamic recrystallization decreased. The peak welding temperature exhibited a significant increase from 285 ℃ to 421 ℃, accompanied by a corresponding reduction in cooling rate from 32.3 ℃/s to 20.2 ℃/s. This change in the welding thermal cycle resulted in significant grain growth, increasing the average grain size at the weld center from 1.4 μm to 8.2 μm. Under the relative high heat input condition, the grains with Goss type 110<001> texture grew rapidly, resulting in the shear texture changed to recrystallized texture. The change of welding thermal cycle did not significantly affect the grain structure and textural type of the weld, and it just affected the final grain size and the proportion of large angle grain boundaries. This microstructural stability of the weld was attributed to the fact that the grain refinement was dominated by continuous dynamic recrystallization throughout a wide range of heat input.