The analysis and model of human skin color is important in many research areas including computer graphics, medical imaging, and cosmetic development. The skin color is influenced with a variety of conditions, such as the mental condition of human's feelings, the physical condition of sunburn, and the medical condition of inflammation. The present paper describes an estimation method of surface-spectral reflectance based on a skin optics model and its application to image rendering of human skin. The human skin is modeled as two layers of turbid materials. The estimation algorithm is based on the Kubelka-Munk equations with unknown five parameters in the two-layers model. These parameters are the regular reflectance at skin surface and the four weights for spectral absorption of such different pigments as melanin, oxy-hemoglobin, deoxy-hemoglobin, and bilirubin. Moreover, the optical coefficients of spectral absorption and scattering for the two skin layers and the thickness values of these layers are used for the solution. Realistic three-dimensional images of a human hand are created using the estimated spectral reflectances and the Torrance-Sparrow reflection model. We execute some experiments for examining the estimation accuracy of skin spectral reflectances and evaluating the computer graphics images of a human hand created under the variety of conditions. The experimental results show the feasibility of the proposed method.