Abstract: The temperature field and the temperature developing history were studied both numerically and experimentally for the conventional TIG welding and TIG welding with a spot heat sink of Ti alloy TC4.Comparing with the "static" control method,in which a temperature field was preset on workpieces,the TIG welding with a spot heat sink was also named dynamically controlled low stress no-distortion (DC-LSND) wel-ding technique,in which the arc was followed with a moving spot heat sink.The results showed that the saddle-backed temperature field was formed near the heat sink in DC-LSND TIG welding.There existed a low temperature region at the zone where the heat sink was applied.The contraction of this zone led to tensile action on the high temperature region nearby,which effectively reduced the incompatible strains and residual tensile stress in the weld,and prevented the occurrence of deformation.The research on the distorted temperature field of DC-LSND welding was the prerequisite to understand the mechanism of controlling deformation by this method.