The use of renewable energy system (RES) is increasing rapidly. However, it is still difficult to measure the environmental impact of renewable energy system. This study aims to develop a general environmental indicator which is able to reflect all the aspects of environmental impacts of a RES. The life cycle assessment (LCA) and fuzzy logic is used to develop an environmental indicator to assess all the environmental impacts. The five important environmental indicators are selected based on LCA standard: Abiotic Depletion Potential, Land Use, Climate Change, Photochemical Ozone Creation Potential and Acidification Potential. Fuzzy inference system is used to convert the original values of these indicators into fuzzy data and aggregate them into the general indicator. The computed fuzzy value of the general indicator is then defuzzified into a crisp number as the final indicator value of environmental impacts.