Reflective thermal insulation coatings are a new type of building materials, which have the functions of heat insulation, energy saving and environmental protection, and have been widely used in external structures of buildings. The performance of reflective thermal insulation coatings is mainly determined by their interaction with solar radiation, that is, the reflective and absorptive capacity of reflective thermal insulation coatings can directly reflect the advantages and disadvantages of their thermal insulation and thermal insulation performance. For specific reflective heat insulation coatings, the spectral characteristics of reflective heat insulation coatings mainly depend on their construction thickness parameters. The variation of construction thickness can directly affect the spectral characteristics of reflective heat insulation coatings, and the variation of construction thickness has a great impact on its construction efficiency. Therefore, the variation of spectral characteristics of reflective heat insulation coatings with thickness parameters is explored to determine the best reflective heat insulation coatings. Construction thickness has important practical and theoretical significance for reducing consumption of materials and optimizing construction technology. In order to quantitatively analyze the influence of construction thickness parameters on the spectral characteristics of reflective heat insulating coatings, the spectral data of the thickness of five types of coatings, 0, 0.5, 1.0, 1.5 and 2.0 mm, were used as data sources. The spectral data were processed and analyzed by the methods of de-envelope, absorption peak depth and subtraction, and the effect rules of thickness parameters on reflective and absorption properties of reflective heat insulating coatings were quantitatively analyzed. The results show that: (1) except for ultraviolet-blue light, the reflectivity of coatings to light decreases with the increase of wavelength, that is, coatings have strong reflectivity to short wave band and strong absorption to long wave band, which indicates that coatings have certain thermal insulation and thermal insulation properties; (2) the increase of coatings thickness helps to improve the thermal insulation performance of coatings, but it is helpless. In order to enhance the thermal insulation performance of coatings, the increase of thickness is helpful to enhance the reflectivity of coatings, but the increase of reflectivity of coatings increases first and then decreases, and the change of absorption peak depth increases first and then decreases. When the thickness reaches 1.0 mm, the reflectivity of coatings tends to be saturated; (3) the thickness of coatings has a significant effect on the depth of absorption Valley and has an effect on absorption. Valley (peak) position plays an important role. When the coating thickness reaches 1.0 mm, the absorption Valley (peak) waveform changes.