This article analyzes the spectral reflection properties of skin surface with make-up foundation. Foundations with different material compositions are painted on a bioskin. First, the authors measure the spectral reflectance of the skin surfaces under a variety of conditions of light incidence and viewing. Second, the authors show the limitations of the model-based approach for describing the reflectance curves by a small number of parameters. A new approach based on the principal component analysis is then proposed for describing the detailed shape of the surface-spectral reflectance function. All skin surfaces exhibit the property of standard dichromatic reflection, so that the observed reflectances are expressed as a linear combination only two spectral components of a constant reflectance and a diffuse reflectance. Moreover, the authors find that the weighting coefficients are decomposed into two basis functions with a single parameter. As a result, the spectral reflectance under arbitrary observation conditions can be estimated by synthesis of the diffuse spectral reflectance and several one-dimensional basis functions. Finally, the feasibility of the proposed approach is examined in detail in experiments using real foundation samples.