Two integrating sphere system using the substitution method have been built to measure the reflectivity of 30CrMnSiA
irradiated by Nd:YAG continuous wave laser with a wavelength of 1064nm.It can prevent the fluctuation of laser output
energy. The back surface temperature was recorded using NiCr-NiAl thermocouples. Surface oxide film composition and
thickness were studied by XPS and XRD. A one-dimensional heat conduction model implementing a parabolic oxide
growth law was developed to obtain the temperature-dependent reflectivity. The computational and experimental results
are well accordant with each other.