The study on redistribution of urban population has always been paying more attention by the academe of domestic and overseas. Since 1980's, with the development of society and economy, the redistribution of urban population in Xi'an has made great changes. So this article makes the research on Xi'an's redistribution of urban population in order to offer some suggestions for urban planning branch to lead urban development reasonable. Based on the data gained from the China's third, fourth and fifth national census (1982,1990 and 2000), from different aspects of population, such as size, density, increasing character and transfer change in different zones, this paper makes a comprehensive study on the spatial redistribution of the population in Xi'an. Farther, reducing the analysis cell to street, village and town, this paper analyzes the difference of population redistribution more clearly. The authors find that Xi'an had formed the differential pattern of "City-core's population decrease, Inner-city and Sub-urban increase in high speed and Ex-urban increase in low speed" in the 1980s; in the 1990s, this pattern in Xi'an became more obvious. The authors select Newling model to forecast the trend of spatial distribution of population density of Xi'an. Through the regressions of spatial distribution Newling models of population density, the authors find that the population density in the City-core decreased constantly from 1982 to 2000 year, but did not form the lower vale in the end of 2000 year, the flood tide of population density in the City-core has the outward process trend, and the max of population density will distribute between rampart and the 2rd ring road in 2010. Lastly, this paper analyses the mechanisms of the redistribution of urban population in Xi'an. The end of this study shows that we should establish the land repaying system, reform the housing system and remake the old city, and carry out subrogation of the urban general planning and constructing and consummating of transport facilities and communication system.