Abstract: X ray diffraction method was used to determine distribution of the surface residual stress in the joints by friction stir welding and tungsten inert gas welding for aluminum alloys.There exist obvious stress variation in two kinds of welds.Distribution of residual stresses in longitudinal direction show W shape.The residual stress droped rapidly outside the friction stir weld.The maximum tensile residual stress exist in the heat affected zone (HAZ).Compared to that of TIG welds in HAZ,the residual stress values of friction stir welds is lower by about 15%-25%.