Steady-state fluorescence was used to obtain a bimolecular rate constant for the reaction between congo red and the known fluorescence quenchers, H2O2, diethylamine, nitromethane and nitrobenzene. The observed bimolecular rate constant correlated quite well with the photo-inducted electron transfer rate constant, kET, which was obtained through the Marcus dielectric continuum theory. The activation energy and the solvent reorganization energy associated with these reactants were also determined. The relation between the distance of sphere of reaction and the electron transfer rate constant will be discussed.