As cities represents the microcosms of global environmental change, it is very important for the global sustainable development by decoupling environmental pressure from economic growth on city level. In this paper, the municipality of Chongqing in China is employed 18 as a case to show whether the decoupling of environmental pressures from economic growth has 19 occurred in cities undergoing rapid economic growth; what is the level of decoupling; and what 20 causes the observed degree of decoupling. Results show the following. (1) During the period of 21 1999-2010, decoupling from economic growth has been absolute for the emissions of SO2, soot, and waste water, while it has been relative for total energy consumption, emissions of CO2 and solid waste. (2) Compared with the period 2000-2005, decoupling level improved for all the six environmental pressures in the period 2005-2010. (3) Compared with China and other three municipalities of China, the overall decoupling level of Chongqing is above China's average while below those of Beijing and Shanghai. (4) During the period 1999-2000, technological change was the dominate factor for decoupling Chongqing's environmental pressure from economic growth, as it contributed 131.4%, 134.6%, 99.9%, 97.7%, 104.5% and 54.9% to the decoupling of total energy consumption, emissions of CO2, SO2, soot, waste water and solid waste, respectively; while economic structural change had very tiny effect to the decoupling of emissions of soot and SO2, and it even had negative effect to that of total energy consumption, and emissions of CO2 and waste water. Based on the above observations, we explain the difference in decoupling levels for different environmental pressures and suggest approaches for policy-makers on further promoting decoupling environmental pressure from economic growth.