Abstract: In this paper, based on the principles of the arc physics and optical spectroscopy, the research on TIG welding arc ultraviolet spectrum has been done, utilizing a system of welding arc ultraviolet spectrum controlled by computer.Distribution feature of arc ultraviolet spectrum in different welding parameters and time distribution feature on some special line of arc ultraviolet spectrum have been acquired. The results show that the distribution feature of welding arc ultraviolet spectrum is linear at background of continuous spectrum. Ultraviolet spectrum distribution and amplitude are different in different welding parameters. With welding current increasing, some shorter wavelength of ultraviolet spectrolines appeared.In measurement range(205~280nm), some separated spectrolines have been observed, and among them the FeⅡ255.50's amplitude is high, and its shape and reappearance is well. At the FeⅡ255.50 nm, the measured ultraviolet radiation of the TIG welding arc is steady distribution in time domain. This provided a basis for utilizing arc spectrum information and researching welding physical process.