Abstract: There are complex relationships between urbanization and ecological environment in different regions and different phases. This paper explores the interactive process and quantitative mechanisms during 1995-2011 in Urumqi，Xinjiang，China. Most of the indicators come from the“Xinjiang Statistical Yearbook”（1996 to 2012），“Urumqi Statistical Yearbook”（1996 to 2012），“Xinjiang city，county building Statistical Yearbook”（1997 to 2011），“Urumqi Water Resources Bulletin”（2000 to 2011），and some other statistical data are from Environmental Protection Bureau and Construction Committee of Urumqi，rest of them was calculated by the authors. The paper describes the comprehensive indexes of urbanization level and ecological environment quality with the Entropy Method，demonstrates causal relationships between comprehensive indexes of urbanization level and ecological environment quality with the co-integration test and Granger causality test，and analyzeses the dynamic process during 1995-2011 with impulse-response function and variance decomposition model. Results show that the urbanization level in Urumqi had been gradually increasing since 1995，and agriculture-disengaging population process and economic growth were its main features，but the comprehensive index of ecological environment quality and its components exhibited different trends. The comprehensive index of urbanization level is the Granger causal reason for the comprehensive indexes of the ecological environment quality，ecological state and ecological response. Urbanization shows unidirectional stress effect on the ecological environment during the research period. Urbanization and ecological environment have not formed the interactively dynamic coupling situation. Promoting the urbanization level，the comprehensive indexes of the ecological environment quality will decrease in the first and then rise slowly under the Impulse Response analysis. The comprehensive indexes of urbanization level pose negative effects on the ecological state，but positive effects on the ecological response. The contribution rates of U to E，S and R are still less than themselves，but the contribution rates are continuous rising. The explanatory power of urbanization to the ecological environment is gradually improved from the long-term forecast. The current energy resource utilization efficiency and environmental investment levels have played an effective role in improving environmental quality. But we should have a rational view on these measures，especially for the urbanization development measures we take to promote the construction of the ecological environment.

Key words: urbanization, ecological environment, quantitative analysis, Urumqi