<p>This study systematically investigates the physical characteristics of high-frequency pulsed twin-tungsten inert gas (HFPT-TIG) arc and the underlying influencing mechanisms. High-speed imaging, arc force measurement, and electrical signal acquisition were carried out to examine the effects of tungsten electrode spacing, arc length, and welding current, as well as high-frequency pulse frequency and amplitude on arc morphology, arc force distribution, and static arc characteristics. The results indicate that, at small electrode spacing, the HFPT-TIG arc exhibits a stable bell-shaped morphology. The superposition of high-frequency pulsed current significantly enhances arc constriction, which is more pronounced when observed from the front camera direction, thereby increasing arc stiffness and effectively suppressing arc lagging under high welding speeds. Compared with conventional TIG and twin-tungsten TIG (T-TIG) arc, HFPT-TIG further enhances penetration capability and arc energy concentration on the basis of the already good humping suppression ability of T-TIG. Moreover, the static characteristic curve of HFPT-TIG arc displays a typical U-shaped profile, with arc voltage values lying between those of TIG and T-TIG arcs. These findings demonstrate that HFPT-TIG welding offers distinct advantages in achieving high penetration capability, high humping resistance, and enhanced process stability, providing a solid physical basis for high-efficiency and high-quality welding of thin-sheet materials.</p>