Abstract: The residual stres for friction stir welded Al alloy LY12 plates at different parameters was studied by using the blind-hole methods.To release the influence on the measuring accuracy of high welding residual stress when the hole drilling method was used, three dimensions finite element model was developed to simulate the test of the strain releasing coefficients.The strain releasing coefficients A and B were corrected based on the energy parameter which was obtained by the FEM analysis results.The results showed that longitudinal residual stresses were asymmetrically distributed at different sides of the weld center and it was high at the advancing side and relatively low at the retreating side.The transversal residual stresses are not equal to zero but about 12.7% of base metal.The residual stresses will become larger firstly and then decrease with the rotation rate increasing and become larger and larger with the pressed-in and welding speed increasing.