Effective urban function partition is the guarantee of the development of a healthy and orderly urban system.Based on the panel and serial statistical data,urban functional zoning and the spatial differentiation in Xi'an have been researched by hierarchical cluster analysis method.Nine districts of Xi'an are divided into six functional zones consisting of the core zone,Yanta,Weiyang,Chang'an,Baqiao and Yanliang-Lintong.Their main development directions are as follows.The core zone which functions as the central business district is characterized by its developed commercial circulation.Yanta District with Xi'an High-tech Industrial Development Zone and Xi'an Qujiang National Culture Industry Demonstration Zone are characterized by their technological economy and cultural industry. Weiyang District is characterized by Xi'an Economic and Technological Development Zone and its industrial economy.Chang'an District is featured by its industry of science, technology and education,which is strengthened by Guodu Industrial Development Zone of Education,Science and Technology and Xi'an National Civil Aerospace Industry Base. Baqiao District is characterized by its development of ecotourism and ecological agriculture area.Xi'an Yanliang National Aviation High-tech Industrial Base and ecological agriculture in Yanliang-Lintong area promote the transition of this area's traditional agriculture.In addition,this paper discusses the driving factors of urban functional zoning and their spatial development differentiation,and explains the comprehensive functions of the primary factors such as urbanization and economic development,historical basis and path dependence, scale economy and accumulative effect,localization and differentiation,and the new factors such as the construction of new economy and development zones,macroeconomic regulation and policy orientation and so on.The primary factors,as auxiliary function, can affect and propel the process to a certain degree,while the new factors,as main function, can transform and promote the advancement to a large extent.Above all,this research helps to get a better understanding of the city development,organize urban activities rationally and further provide some practical references for other cities.