Abstract: The welding distortion and changing law of alum-inumalloy thin wall cone were investigated by means of model test,automaticpulse tungsten inert gas welding.The results showed that the welding distortion was mainly deflection deformation and change of circumference.The maximum deflection of cone structure welded with argon shield was smaller than that welded with argon and helium mixture.The deflection was analyzed with resolving method,the influence of the welding process on deflection was proposed,and the verification data had been provided for numerical simulation of thin wall cone structure,moreover,the exper-imental basis had been provided for reduction and controlling of welding distortion.