There are strict logic and profound philosophy in the “ten principles” of Xi Jinping Thought on Ecological Civilization, which are constructed on the basis of Marxist view of nature, epistemology and practical methodology. Starting from the view of nature that man and nature coexist harmoniously, the “ten principles” have answered the question “why ecological civilization should be built”. Based on the concepts on ecological history, ecological development and ecological people’s livelihood, the “ten principles” have constructed the theory on building “what kind of ecological civilization” in terms of its form, way of development and stance. Guided by the methodology of ecological political leadership, ecological system governance, ecological rule of law, ecological national action and ecological global win-win view, the “ten principles” have provided answers to the question of “how to build ecological civilization”. The “ten principles” serve not only as a general guidance for building a beautiful China, but also as a Chinese concept and approach for building a beautiful world and constructing developing countries’ ecological civilization.