The flux utilization rate of light source is an important evaluation index of light distribution elements in the illumination optics design. Based on Fresnel formula, a theoretical model for reflection-absorption loss of light distribution elements is established, and its applicable range is discussed. Using this model, the reflection-absorption loss of the free-form surface plano-convex lens and the total-internal-reflection lens are calculated respectively, and the results are compared with those obtained by software simulation and experimental measurement. It is found that the calculated values of the theoretical model are highly consistent with the simulated results of the optical software,and the absolute errors of the transmissivity of free-form surface plano-convex lens and total-internal-reflection lens with collecting angle 60° for point source are 0.7% and 0.14% respectively. In the other hand, considering the influence of the assembly error, the calculated values are also basically consistent with the experimental measurement results. Based on this research, it is indicated that by using the established reflection-absorption loss model, in the illumination optics design, the reflection loss on each optical surface and the material absorption loss of various light distribution elements can be predicted quickly and accurately without software simulation and experimental test. This provides a reference for the performance evaluation, structure selection and optimization of light distribution elements.