Abstract: This paper investigates the influence of ternary shielding gas with different component ratios on the welding joint of GTAW Inconel 690 alloy. The welding process was simulated using ANSYS Fluent software, and analysis was conducted employing high-speed photography and macroscopic weld pool morphology. The conclusions are as follows: Based on simulations of arc temperature and arc pressure, as the proportion of helium increases, the weld pool temperature gradually rises, from 21, 000 K with 80%Ar+15%He+5%H₂ to 24, 000 K with 20%Ar+75%He+5%H₂. The arc pressure initially increases and then slightly decreases, while the voltage progressively rises. Analysis via high-speed photography reveals that the arc profile in the ternary gas mixture with added H₂ assumes a mountain-peak shape. Furthermore, as the He content increases, this mountain-peak-shaped arc gradually contracts. With the arc compression, the post-weld pool temperature increases, and both the weld pool width and depth progressively increase.