Low cycle loading testing method with the PWS-100 low frequency fatigue machine and high cycle loading testing method with the QBG-100 high frequency fatigue machine were used to test the A6605-T6 aluminum alloy welded joints. The dynamic strain test machine was used to test the strain value of the above two fatigue method. The results showed that the strain value of No.1,4, all changed after the first time loading under the low cycle loading method but the strain value didn’t change after second time loading to10 million times loading. With the cycle times have changed from 10 thousand times to 10 million times,the strain value of N0.1,4, didn’t change. So the results showed that the welded joints didn’t show new plastic deformation with the increase of the cycle times,so the welding residual stress didn’t continue to relax with the incrrease of the cycle times.