When the external high-power laser invades the target surface, the coating will produce self-activation response to the laser, and the surface reflectivity will increase rapidly, reflecting most of the laser energy, so as to achieve the effect of target protection. Therefore, the surface reflectance is an important parameter to evaluate the laser ablation resistance for the self-activated intelligent laser protective coatings. The reflectance measuring methods for coating surface can be roughly divided into two categories: the first is to evaluate the reflection and absorption of laser by studying the changes of material state or measuring the temperature change of the material before and after absorbing the laser in the irradiated region. The main method is the laser absorption calorimeter [18; 19; 20; 21; 22]; The second is to measure the reflectivity of materials from the optical point of view, usually using the integrating sphere measuring method [23; 24; 25; 26; 27; 28]. Among these two reflectivity measurement methods, although the laser calorimeter can quantitatively measure the reflectivity of materials, it has some limitations. First of all, when the calorimetry is used to measure, it is usually assumed that the light energy absorbed by the material is totally converted into the heat energy, that is, the light energy absorbed by the material can be equivalent to a certain heat flux injection. However, the heat exchange between the material and the external environment is ignored in the measuring process, leading to the large errors compared with the real results. Secondly, the calorimetric method can only measure the reflectance for a small number of materials meeting the lumped parameter conditions. It is difficult to determine the reflectance for other types of materials. Compared with the laser calorimeter method, the method of integrating sphere has higher accuracy thanks to its high efficient collection for the scattering light. However, the current integrating sphere reflectance measurement system has some defects: Firstly, the laser wavelengths used for the reflectivity measurement are limited, most of them can only response to the wavelength from ultraviolet to visible light, instead of the range from near-infrared to far-infrared band. Secondly, the measuring region is always discontinuous, so it is impossible to measure the scattering rate in a specific region on the coating surface. Thirdly, the measuring accuracy still needs to be improved. The reflectivity measurement accuracy of the current integrating sphere system is less than 3-5% [29; 30; 31; 32]. In order to realize the high-precision measurement of the scattering rate for specific damage region on the coating surface in infrared band, a material-surface-scattering-rate measurement system responded to the infrared laser was proposed based on the three-hole integrating sphere. First of all, according to the structure characteristics of three-hole integrating sphere and the Lambert diffuse reflection model, the quantitative relationship between the scattering rate of material surface and the incident light power was given theoretically. Then, the main factors affecting the measuring accuracy of the system were analyzed and simulated by using the TracePro tool [33]. The correctness of the simulation analysis results was verified by the experiments. Finally, through the establishment of a high-precision three-hole integrating sphere scattering rate experimental measurement system, and combined with the results of TracePro simulation analysis, the uncertainty sources and interfering factors from the laser power stability, the laser incidence angle, the gap between the sample and the hole of integrating sphere, and the ambient light were comparatively analyzed. The maximum measuring relative uncertainty of the system was found to be less than \(\pm\)2.22%.