In this paper, dominant factors influencing the weld angular distortion were discussed on the theoretical basis of the relation between weld angular distortion and distribution of inherent strain for the more accurate quantifying and managing the weld angular distortion. Based on the experimentally observed relation between highest temperature and inherent strain distributions, the mechanical melting zone was focused as the temperature distribution corresponding the generation area of inherent strain controlling the weld angular distortion. TIG bead-on-plate welding of high tensile strength structural steel was performed under the various welding conditions to investigate the effect of welding conditions on the weld angular distortion. And then the weld angular distortion was arranged by the conventional parameters of weld penetration and weld heat input, and the newly proposed parameter of the mechanical melting zone. As the results, it was confirmed that the weld angular distortion could be arranged more coordinately by the proposed parameter of mechanical melting zone rather than the conventional parameters of weld penetration and weld heat input. Thus, it was concluded that the mechanical melting zone should be focused as temperature distribution controlling the weld angular distortion for the more accurate quantifying and managing the weld angular distortion.