Abstract: The ultrasonic impact treatment on the thin 6061 aluminum alloy plate without and with welding residual stress was analyzed by means of the finite element software ANSYS.The simulated result was compared with the tested one.In the case of the existence of no welding residual stress,the result shows that the surface stresses are compressive at the impact center, and tensile around the center after treatment.Along the depth of the sample,compressive stresses turn into tensile ones.The whole stress state increases gradually with the treatment.In the case of the existence of welding residual stress,with the increase of the displacement load,stresses at the impact zone decrease greatly and the highest stress locates the area away from the weld.The simulated result of the stress change accords well with the tested one.