Abstract: Acoustic field analysis of space wave propagation used for ultrasonic-aided TIG welding was proposed and finite element simulation analysis of sound field variation with acoustic emission radius and that of the acoustics parameters variation with arc length was employed with COMSOL. Besides,a new model was also established for ultrasound-aided TIG welding characteristics. Distribution of arc pressure for stable combustion DC U-TIG arc and that of conventional TIG arc under different welding parameters were measured experimentally by using a hole drilling method. The result reveals that arc peak pressure of DC U-TIG is significantly higher than that of conventional TIG, which illustrates that the effect of hybrid-arc can enhance the arc pressure above the surface of weld pool,but the D-value between them decreases with the welding current increases. Preliminary analysis suggests that when high welding current is employed, the high temperature and large current density in the central area of arc column greatly improve the arc peak pressure of conventional TIG. In contrast,the increase of arc peak pressure is reduced with the increase of weld current because plasma flow force of welding arc is limited by gas-flow rates.