Low-power laser radiation can be used to influence an arc welding process with the aim of stabilisation or guiding the arc attachment at the workpiece. Recent studies showed that resonant radiation absorption can be beneficial compared with infrared radiation. The latter is mostly absorbed at the workpiece surface, whereas laser radiation in the range of arc line radiation can have an explicit impact on the arc. The absorption of laser radiation in the range around 811 nm and laser power up to 400 W by a tungsten inert gas (TIG) arc is studied systematically by spectroscopic, radiation power and voltage measurements. For a TIG arc at 120 A, considerable radiation absorption is found whereas arc voltage is changed by some millivolt, and line emission coefficients change mainly in the outer part of the arc.