Abstract: The thermodynamics behavior of arc is a key factor affecting the flow of molten pool and welding quality. High-speed photography and numerical simulation were used to systematically analyze the influence of the characteristics of hollow tungsten electrode and solid electrode on the thermal distribution characteristics of arc. The results showed that when the welding current was 350 A, the solid tungsten electrode weld exhibited deep and narrow weld formation characteristics, while the hollow tungsten electrode weld exhibited shallow and wide weld formation characteristics. At a distance of 1 mm from the surface of the test plate, both the temperature and pressure fields along the horizontal direction of the solid tungsten electrode and the hollow tungsten electrode arc exhibit typical Gaussian distribution characteristics, and the temperature and pressure values of the hollow tungsten electrode arc at the center position are 61.9% and 23.5% of those of the solid tungsten electrode, respectively. The pressure distribution of solid tungsten electrode arc on the central axis is U-shaped, while the pressure distribution of hollow tungsten electrode arc is N-shaped. The constructed strong coupling analysis model for arc and molten pool has good consistency with the actual situation, which can used to analyze and forecast the thermodynamics behavior of arc and molten pool.