Objective To study the application of metameric black in spectral dimension reduction. Methods MBPCA spectral dimension reduction method was put forward based on metamerism black spectral characteristics. This method decomposed the color spectrum into basic spectrum and metameric black spectrum. The basis vectors of basic spectrum consisted of the first three basis vectors of original spectrum by PCA. The residue spectrum between original spectrum and basic spectrum was metameric black spectrum. The basis vectors of metameric black were derived from the residue spectrum by PCA. Results When the dimension reduction illuminant was in accordance with lighting illuminant, once the number of basis vectors was above three, the color differences of MBPCA were zero. When the number of basis vectors was six, the average color differences were close to one. Conclusion Compared with PCA, the spectral accuracy of MBPCA was close to that of PCA, and the colorimetric accuracy of MBPCA was higher than that of PCA. The six-dimensional model built by MBPCA could effectively meet the needs of spectral color reproduction.