Abstract: The effect of environment pressure on hyperbaric TIG (tungsten inert-gas)welding arc cannot be neglected.The arc temperature is one of the most important parameters.It has important significance to measure the temperature of hyperbaric TIG welding arc in understanding physical property of hyperbaric welding arc and seeking improvement of the quality of underwater hyperbaric welding.The spectral diagnostics was introduced, and the TIG welding arc in high-pressure was analyzed.A set of feasible method of highpressure arc temperature measurement was established.The welding arc temperature in high-pressure was analyzed, and the function between the environment pressure and the arc temperature was established. The experimental result was analyzed.This research is significant and valuable to the study of hyperbaric welding arc physics.