Abstract: Formation and relief mechanism of welding residual stress were addressed.Compressive plastic strain dose not play a role in the formation of welding residual stress.The residual stress is produced by the contraction of weld metal and its vicinity during the cooling process at the temperature below its "mechanical melting point".Residual stress elimination does not employ the tensile plastic strain to reduce, withdraw or compensate the compressive plastic strain, but to convert the residual elastic strain to a plastic one.The elimination of the inherent strain is not a prerequisite to eliminate welding residual stress.Partly removed or completely held inherent residual strains can also completely eliminated the residual stress.A new method is proposed to perform heating treatment following the welding torch to control stress-strain precisely, to realize the stress free welding or stress-free and non-distortion welding or even proper compressive stress and non-distortion welding or large compressive stress and minor distortion welding.The result is also compared with the traditional processing method and finite element analysis.