Abstract: A hybrid life cycle assessment method based on the carbon footprint theory is described in this paper to analyze the greenhouse gas emissions of large hydropower projects throughout their whole life cycle, focusing on demonstration of their effects on carbon emission reduction. This method, in application to the overall layout scheme of concrete gravity structures for a huge hydropower project, considers four stages of its life cycle: material and equipment production, transportation, construction, and operation and maintenance. The results show a total carbon emission of 1145.49×104t CO2e, average annual emissions of 25.46×104t CO2e, and carbon emission factor of 14.09g CO2e/kWh, which are on a level of only 1.71 percent of the corresponding coal power plant's emission. From high to low percentage of contribution to the total CO2 emission at the four stages, operation and maintenance stage of 50% comes first, then production stage of 45% and construction stage of 3%, and last transportation stage of 2%. Thus, to lower the emission, the use of cement and steel should be reduced, the construction technology of filling and excavation be improved, and the reservoir be cleaned up. This study provides more evidences that large-scale hydropower projects are clean energy resources.