Differential diagnosis of human colon adenoma was studied using the Kubelka-Munk spectral function of the DNA and protein absorption bands at 260 and 280 nm in vitro. Diffuse reflectance spectra of tissue were measured using a spectrophotometer with an integrating sphere attachment. The results of measurement showed that for the spectral range from 590 to 1 064 nm pathological changes of colon epithelial tissues were induced so that there were significant differences in the averaged values of the Kubelka-Munk function f(r∞) and logarithmic Kubelka-Munk function log［f(r∞)］ of the DNA absorption bands at 260 nm between normal and adenomatous colon epithelial tissues, and the differences were 218% (p＜0.05) and 68.5% (p＜0.05) respectively. Pathological changes of colon epithelial tissues were induced so that there were significant differences in the averaged values of the Kubelka-Munk function f(r∞) and logarithmic Kubelka-Munk function log［f(r∞)］ of the protein absorption bands at 280 nm between normal and adenomatous colon epithelial tissues, and the differences were 208%(p＜0.05) and 59.0%(p＜0.05) respectively. Pathological changes of colon epithelial tissues were induced so that there were significant differences in the averaged values of the Kubelka-Munk function f(r∞) and logarithmic Kubelka-Munk function log［f(r∞)］ of the β-carotene absorption bands at 480 nm between normal and adenomatous colon epithelial tissues, and the differences were 41.7%(p＜0.05) and 32.9%(p＜0.05) respectively. Obviously, pathological changes of colon epithelial tissues were induced so that there were significant changes in the contents of the DNA, protein and β-carotene of colon epithelial tissues. The conclusion can be applied to rapid, low-cost and noninvasive optical biopsy of colon adenoma, and provides a useful reference.