Using high-temperature pure iron (DT8) as the research object, the spectral irradiation intensity properties of DT8 at temperatures ranging from 1510 to 1620°C were analysed. The luminescence spectrum of DT8 exhibited four characteristic peaks within the measured wavelength range. The corresponding wavelength ranges were 588–590, 765–770, 940–950, and 960–970 nm. The peaks in each wavelength range decreased significantly with decreasing temperature. The luminescence spectrum of DT8 was further investigated using a multiple-peak fit, and a mathematical model of the spectrum was created using the link between the fitted peak parameters and the temperature. Error analysis was performed on the model-calculated and original spectra after supplementation, and the error evaluation index, R, of the actual measured and model-calculated spectra was defined. Through calculations, it was determined that the degree of coincidence, R, between the calculated results of the model and the actual measured results was >99.1%, whereas R increased slightly with an increase in temperature.