To process the challenge new environment brings to urban drainage system,a scientific and systematic quantization index system is needed to assess the sustainability and rationality of drainage system and to compare different kinds of drainage systems.Based on comprehensive evaluation and life cycle assessment (LCA),establishment principle,methods and procedures of urban drainage quantization index system are put forward,and the urban drainage quantization index system are built from aspects of environment,economy,technical function and social benefit.Finally,the weight of each index is discussed.The index system can provide data support to the design,management and policy decision for urban drainage system.