This paper discussed population density simulation of shanghai central city in 1990-2000 based on land use, and analyzed the population distribution and change. Some steps were introduced to simulation process to improve precision, such as zoning by cluster analysis, modeling separately by zoning, gradually eliminating errors and precision controlling by street zones. Then the temporal and spatial characteristics of population density change were analyzed based on GIS. Raster overlay produced a map of population density change; concentric circle method and sector analysis method were used to show the distribution characteristics different with distance and orientation; the relationship between population density and residential land use shows the improvement of living condition in Shanghai from 1990 to 2000.