From a biophysical systems perspective, this research suggested using emergy synthesis to highlight the fact that the three constituents of vulnerability are inseparable entities. This also allows for the use of emergy as a common unit to integrate the energetic flows between natural and human society for vulnerability assessment. The properties of exposure, sensitivity, and adaptive capacity are interrelated and overlapping, meaning that in each assessment of vulnerability no single property must be emphasized over the others. The major challenges of incorporating emergy evaluation for vulnerability assessment include: linking biophysical and social realms and their mutual interactions; taking into account the interactive characteristics among the three components of vulnerability; and evaluating these three components with comparable emergy units. On the basis of emergy concepts, the purpose of this paper is to develop a systemic evaluation framework that will help us to interpret the three components of urban vulnerability to flooding from emergy concepts; develop emergy indices to assess urban vulnerability to flooding; and exhibit the spatial heterogeneity of urban vulnerability to flooding via GIS. The pro-posed framework is applied to study Taiwan’s western coastal plain area. The remainder of this paper will first describe our study design and methodology of how emergy concept is used to interpret the three components of vulnerability and the development of emergy indices for assessing urban flooding vulnerability. The frameworkof emergy evaluation and indices is applied to the study area to reveal the spatiality of exposure, sensitivity and adaptive capacity. The advantages and limitations of using emergy evaluation to assess vulnerability are also discussed.