The activated sludge process is very complex ,so the simulation and mathematical models are very useful tool to explain some biological reaction in wastewater treatment. The goal of this research is using ASM1which determined by IWA Task Group to promote development and facilitate the application of municipal biological wastewater treatment system, to studying of reducing the pollution (COD-N) with time in bench-scale SBR. ASM1 was available in special environment program such BioWin- WEST-STOAT-SIMBA-GPSX-EFOR, and this programs are not available on our country, thus this work is returning back to original Model formulation and formulating the matrix on MATLAB like mathematical simulation with possibility of changing The Kinetic parameters and wastewater component according to our local condition.