Gamut mapping is the key element to get satisfactory image reproduction. First, a practical method is used to realize the transform from RGB values of CRT monitor to spectral tristimulus values. The printing paper gamut is predicted by Beer′s law. Further, a non-linear compression method is proposed to realize the gamut mapping. At the same time, the virtual gamut is defined and studied. The result indicates that this model has good practicality for the CMS (Color Management System) of digital photofinishing. This method is applied to high-technology industry with satisfying performance.