Abstract: An axisymmetric model based on the magnetohydrodynamic (MHD) is established to investigate the effect of hydrogen on heat transfer and fluid flow characteristics of argon plasma in GTAW. The profiles of temperature and voltage drop, distributions of arc pressure and current density are simulated by utilizing the fluid dynamic theory coupled with Maxwell equations. The quantitative analysis and comparison of anodic heat fluxes under pure argon and mixtures of argon and hydrogen are also obtained. The results show that the addition of 10% hydrogen to argon makes the arc slightly constricted and increases electromagnetic forces up to 2 times of the conventional arc. Meanwhile, it also increases the temperature, plasma flow velocity, arc voltage, current density. This leads to more energy transferred to the anode, which can partly improve the thermal efficiency. The present study may provide theoretical reference for the further applications of high efficiency GTAW process.