Through the case of the Three-River-Source National Park, this study mobilizes the concept of sociotechnical imaginaries to scrutinize how China’s ecological civilization as an application of sustainable imaginaries is materialized into national parks. Drawing on the extensive literature of science and technology studies that conceptualizes sociotechnical imaginaries as a vision of an ideal future, this study opens the perspective on the complex relationship between sustainable imaginaries and national parks. By combining content analysis of Chinese policies with semi-structured interviews, this study highlights translation and coordination as the most critical elements in realizing the materialization of ecological civilization. Furthermore, the ecological civilization mobilizes various policy instruments to materialize the national park as its materialized imaginary. Finally, the ecological civilization has shaped China’s specific discourse on sustainable development and has been put into practice through national parks.