The study presents ideas and test results related to an unconventional method of MAG welding process monitoring making use of welding arc radiation in the visible range. The experiments conducted indicate the direction of further research on the phenomenon of welding arc radiation and the possibilities of using it for on-line monitoring of other welding processes. The recording of spectral distribution was made using a spectrophotometric card. The stability of a welding process was assessed using the least squares method. The recorded signals were modelled using polynomials and the optimum polynomial order was selected using the F-test method. The study presents the impact of welding current intensity and of a filler metal type on the distribution of a welding arc visible radiation spectrum.