The analysis of diffuse reflectance spectra of skin using a multi-layered model is applied to a variety of fields. Skin has complex multi-layered structure and the penetration depth of the detected light depends upon the wavelength dependence of the optical properties of each layer. It is important to consider the wavelength dependence of the penetration depth of the detected light in order to analyse the diffuse reflectance spectra of the skin. In this study, the photon vanishment in multi-layered model is calculated by Monte Carlo simulation to estimate the contribution of absorption in each layer to diffuse reflectance spectra. We analyse the influence of the anatomical structure of skin and the geometry of detection system on the contribution of each layer to diffuse reflectance spectra. The results are compared with the reflectance spectra of human skin and lip of four volunteers measured with a fibre probe and an integrating sphere. The proposed models of skin and lip can reasonably represent the difference in the spectra between the fibre probe and the integrating sphere. The change in penetration depth of detected light caused by the detection systems depends upon wavelength and it causes the differences in the diffuse reflectance spectra.