Abstract: The fatigue performance of friction stir welding(FSW) joints is a key factor to ensure their structural reliability, which can be characterized by the stress-life curve(S-N curve). For FSW joints under different welding conditions,the S-N curve should be measured separately. The fatigue properties of 6005A-T6 aluminum alloy FSW joints were analyzed by fatigue tests of some welding specimens, and the S-N curves under different survival rates were estimated. In addition, the influence of thickness on the fatigue performance of FSW joints was analyzed, and the specimens with 8 mm and 16 mm thickness were compared. The results show that the S-N curves with more than 95% survival rates at 95% confidence can be used to guide the anti-fatigue design. The thickness has little influence on the ultimate fatigue strength in the long-life zone,but the characteristics of S-N curves of FSW joints with various thickness are different. The 16 mm thick joint has a longer fatigue life at high stress level and a steeper S-N curve compared to the 8 mm thick FSW joint.