The photocatalytic degradation of C I Basic Blue 3 (BB3) in water on supported TiO2 nanoparticles was carried out in a rectangular flat-plate photoreactor The photocatalytic degradation kinetic characteristics were experimentally investigated under different light intensities and initial dye concentrations Calculating corresponding "apparent adsorption constants", K-s, and "apparent rate constants", k(r), of experimental results according to the Langmuir-Hinshelwood (L-H) model emphasized that the L-H constants varied with regard to the light intensity A new kinetic model was developed on the basis of the intrinsic element reactions which took into account the effect of light intensity, reaction intermediates, organic compound content, and first order reaction kinetics The new kinetic model described the experimental results in a more accurate way and explained consistently the dependence of the apparent kinetic parameters k(r) and K-s on the light intensity