Abstract: In this paper,a structured biological kinetic model for activated sludge process is proposed,which is the modification of IAWPRC model with respect to carbonaceous organic pollutants removal. A systematic modeling approach is suggested and applied. The modified model is concisely presented with a conceptual schematic diagram and the matrix format which conveys all the qualitative and quantitative information of the model in s small space, and enable one to easily follow the modeler’s idea. The experimental methods for parameter estimate and the results of determination are also briefly introduced.