The local plastic deformation and redistribution of residual stress would occur under the superposition of static load stress and welding residual stress. The peak residual stress will decrease after the static stress unloaded. This paper was based on this theory and took A6005 A-T6 aluminum alloys welded joints as the objectives to study the static loading conditions and gradual loading conditions under the evolution of residual stress. The results showed that the residual stress had relaxed in high degree after static load stress（the loading stress was 150 MPa）,the peak value had changed from 125 MPa to 48 MPa of the longitudinal residual stress and the peak value had changed from 155 MPa to 56 MPa of the transverse residual stress. The reason was that the residual stress had relaxed due to the superimposion of external load and residual stress beyond the yield strength of the material had been plastic deformation. The welded structures could be statically stretched in some degree before using and could remove some residual stress especially the peak residual stress.