The　existing　research　of　welding　arc　mainly　focuses　on　the　stable　combustion　state　and　the　research　on　the　mechanism　of　welding　arc　ignition　process　is　quite　lack.　The　tungsten　inert　gas(TIG)　touch　arc　ignition　process　is　observed　via　a　high　speed　camera　and　the　high　time　resolution　spectral　diagnosis　system.　The　changing　phenomenon　of　main　ionized　element　provided　the　electrons　in　the　arc　ignition　is　found.　The　metallic　element　is　the　main　contributor　to　provide　the　electrons　at　the　beginning　of　the　discharging,　and　then　the　excitated　shielding　gas　element　replaces　the　function　of　the　metallic　element.　The　electron　density　during　the　period　of　the　arc　ignition　is　calculated　by　the　Stark-broadened　lines　of　H-alpha.　Through　the　discussion　with　the　repeatability　in　relaxation　phenomenon,　the　statistical　regularity　in　the　arc　ignition　process　is　analyzed.　The　similar　rules　as　above　are　observed　through　the　comparison　with　the　laser-assisted　arc　ignition　experiments　and　the　metal　inert　gas(MIG)　arc　ignition　experiments.　This　research　is　helpful　to　further　understanding　on　the　generation　mechanism　of　welding　arc　ignition　and　also　has　a　certain　academic　and　practical　significance　on　enriching　the　welding　physical　theoretical　foundation　and　improving　the　precise　monitoring　on　automatic　arc　welding　process.