This study aims to provide useful information when making a decision for the environmental and economic efficiency assessment of infrastructure, based on Life Cycle Assessment(LCA). It estimates environmental cost on environmental pollutants that are possible to happen by locations and by types of emergency spillway for korean multipurpose dam, which is selected as a study case. For this purpose, this study examines the theories of LCA and Contingent Valuation Method(CVM) and suggests an analysis model of environmental cost. To apply the suggested analysis model of environmental cost for infrastructure to the case study of emergency spillway at the multipurpose dam, this study calculates environmental load on environmental pollutants that generate during life cycle, converts it to a cost to predict environmental cost, evaluates environmental economy of emergency spillway by the estimated result, and draws the optimum alternative that is environmental-friendly and economic.