Abstract: There was complex relationship between urbanization subsystem and ecological environment subsystem in different regions and different phases. This paper explores the interactive process and quantitative mechanism of urbanization and desertification reversal trend during 2003-2013 in Yanchi, a typical area of desertification reversed of Ningxia, China. The paper measures the comprehensive level and dimension of urbanization and desertification reversal with entropy method, examines causal relationships between sub-indexes with ADF stationary test and Granger causality test, and analyzes the dynamic process during 2003-2013 with impulse response and variance decomposition of VAR model. Results showed that:(1) The urbanization level in Yanchi had been gradually increasing since 2003, meanwhile the desertification reversal index remained at more than 0.3. (2) The comprehensive index of urbanization did not directly affect the desertification reversal trend, but its component indicators impacted the desertification reversal trend, pressure, status and response. (3) The explanatory power of urbanization to desertification reversal was gradually improving. Population migration, economic growth, social progress and urbanization development impact on desertification reversal trend, pressure, state, response were maintained at the level of 78%, 58%, 13% and 9%, respectively. As an effective way to improve the ecological environment of inland arid area, the population urbanization and society urbanization should be regarded as the key breakthrough to enhance the urbanization's positive effect to ecological environment in Yanchi County.

Key words: urbanization, desertification reversal trend, Granger causality test, VAR model, Yanchi County