The mathematical fundamentals have been established, based upon principal component analysis, for the estimatimation of the spectral density distributions of two dyes from those of their mixtures. Thougth the spectral density distributions of component dyes cannot be determined uniquely, their possible shapes have been estimated by supposing two physically reasonable assumptions. The suitable computer programs for this purpose have been developed for an IBM-1130 Computer in FORTRAN IV language. Some practical applications are demonstrated here; the influence of width between two peaks of component dyes, the influence of sample number of mixtures, and so forth.