Abstract: The Anaerobic Digestion Model No.1(ADM1)proposed in Feb.2002 by the International Water Association(IWA)is introduced.As a tool to simulate and optimize the anaerobic digestion,ADM1 mainly describes the biological and physiochemical processes occurzed in anaerobic digestion, in which 7 kinds of microorganisms,19 dynamic biological sub-processes,3 gas-liquid transfer kinetic processes,totally 26 dynamic components and 8 implicit algebraic variables are included.Meanwhile,it provides an opening modeling platform and interfaces with activated sludge model (ASM)and thus can be widely used in the simulation of combined anaerobic-aerobic processes.