Abstract: A newly developed method for dynamic in process control of welding stress and distortion of thin-walled structural elements is discussed in this paper.The DynamiCally Controlled Low Stress Non-Distortion(D.C.LSND) welding process provides a tensile effect created by a local spot intensive cooling of just solidified weld while it is still at the high temperature state. This localized tensile effect following the welding heat source dynamically and quantitatively controls the formation of incompatible compressive plastic strain and thermal stress during the welding process.A new device of multi-source(heat source-heat sink) system have been developed.Experiments show that good results of low residual stress levels and complete freedom from distortion can be achieved. It promises a wide prospect for engineering application of non-distortion welding for thin-walled structures.