Abstract: Fatigue crack growth rate is the macroscopic and external performance of the internal structure of the material. Microstructure and residual stress have a significant effect on the growth of macroscopic fatigue cracks.In this paper, the fatigue crack growth rate of different areas of 2A12-T4 aluminum alloy friction stir welding is studied.The results show that: in the weld area, due to the strong mechanical and welding heat action of the stirring pin, the material structure changes, accompanied by the generation of residual stress, resulting in significant differences in the growth rate of cracks in different areas.At low ΔK, the heat-affected zone and the fatigue crack growth rate perpendicular to the weld are basically the same, and both are higher than the crack growth rate along the weld.At high ΔK, the growth rate perpendicular to the weld seam direction is gradually higher than the heat-affected zone rate. At this time, the crack growth rate in these two regions is still higher than the crack growth rate along the weld seam direction.