In the Gas Pool Coupled Activating TIG (GPCA-TIG) welding, double shielding gases are employed to dramatically enhance the weld penetration, the inner inert gas to protect tungsten electrode and molten pool metal and the outer active gas to introduce activating element oxygen. In order to examine the effects of V-groove on the arc characteristics of GPCA-TIG welding in different groove angles and welding currents, probe method, static hole method and thermocouple method were used to obtain the distributions of current density, arc pressure and temperature on the arc anode, respectively. The experimental results indicate that, in the process of groove welding, the peak current density is on both side surfaces of the groove when the groove angle is 90, while the peak of 120° groove is just below the electrode. The maximum arc pressure is located just below the electrode no matter what angle and welding current are. The temperature distribution in groove welding is similar to the current density distribution. The peak temperature is on the side surface in 90° groove, and just beneath the electrode in 120° groove. Besides, all the current density, arc pressure and temperature distribution present different dependence on arc current for different groove angles. The weakened deep weld penetration compared to that without groove results from the change of arc characteristics in the grooved GPCA-TIG welding.