Xi Deli started working at Tsinghua University in 1964 after graduating from the same university. He was transffered from the Department of Chemical Engineering to the Department of Environmental Engineering in 1988. He was committed to the teaching and research in the field of waste water contol, air pollution control and clean production. He was the first to offer the "Clean Production" course in China. He was the director of the Division of Air Pollution and Its Control and an expert for the China Council for International Cooperation on Environment and Development. He retired in 1999 as a professor.