The effects of combined scouring-bleaching and reactive dyeing were investigated by characterizing the functional groups changed of cotton, betel nut, banana and jute fibers using caustic soda, Hydrogen peroxide and reactive dyestuffs. FTIR ATR spectroscopy provided a fast and semi-quantitative assessment of the removal of pectin, lignin, Hemicelluloses, oil, waxes etc on those fibers surface by comparing the changes in intensity of the carbonyl peak induced by Hydrogen peroxide and caustic soda treatments well as bond changing in reactive dyeing around 4000 cm-1. Above all fibers are not reacting identically during changing impurities and covalent bond forming between cellulose and reactive dyes.