Irradiated by a continuous wave (CW) DF laser with power of ～30 kW, wavelength of 3.8 μm, and irradiation time of 1 s, under the conditions of the laser beam approximately perpendicular to the coaxially rounded reflector, the thermal distortions of 3.8/0.633 μm dual-wavebands multi-layer high-power laser reflectors manufactured by different crafts are tested by a Shack-Hartmann wave-front sensor. Based on the thermal conduction equations and thermal-elastic equations, taken account of the thermal effect of the refractivity of the air, a finite element method is used to estimate the thermal absorptions of the reflectors. The results indicate that the lowest thermal absorpaility of the reflectors manufactured with best crafts is approached to 80×10-6. On account of the materials and the structure designs of the coatings being all complete the same, the purpose of the film-plating parameters estimate and/or evaluating is realized.