Study of the roughness effect on the normal spectral emissivity of GH3044

•A computational method for estimating the effect of roughness on the normal spectral emissivity of superalloys was established based on constructing randomly rough surfaces.•The effect of roughness on four emissivity models commonly used in multispectral radiometric thermometry (MRT) was computationally evaluated.•The computational method was verified based on the normal spectral emissivity of GH3044 superalloy with different rough surfaces at 300 K and high temperatures.