The MEDIUM project brings together European and Chinese entities (research centres, universities and companies), which work on sustainable urban development in China. Focusing on a large city and two medium-sized cities (1 to 3 million inhabitants), Hangzhou, Zhuhai and Datong, the project's innovation is twofold: first it addresses urban sustainability from a socio-economic dimension and not only through the prism of environmental issues. Second it operates in fast-developing urban areas overlooked by scholars in comparison with China largest cities.MEDIUM gathers researchers with very different backgrounds and interests, among which urban governance, strategic planning, urban mobility, inclusion of migrants, ICT or networks of multinational corporations. Applying various approaches and methodologies, the project will contribute to better understand urban development dynamics in Chinese medium-sized cities so as to inform decision-makers and economic actors. It will allow innovative ideas to emerge and give rise to alternative patterns of urban development, smart, sustainable and socially inclusive.