Abstract: Through adjusting welding parameters such as welding current, arc length and gas flow rate, the spectral distributions of TIG welding arcwere collected.In order to explore the variation of arc radiation in different spectral zone, TIG welding processes of steel and aluminum were studied for spectral distribution analy sis, respeetively.For TIG welding of steel, the light radiation increases with the arc length in different spectral zone, among which the radiation intensity in spectral zones with less line spectrum increase linearly with the arc length.However, the change law is different for long arc and short arc.The light radiation increases with the growth of welding current.The light radiation is nearly the same when the gas flow rate was in a rather large value.When the gas flow rate was low which can not provide enough protection for the welding arc, the light radiation is affected obviously.For TIG welding of aluminum, the light radiation does not change a lot with the arc length variation. The radiation increases with the growth of welding current.The gas flow rate has great effect on the light radiation of arc when it is low, while has less effect on the light radiation of arc when it is high.