Abstract: When the rate of land expansion was faster than that of population growth, the overall population density would decrease in urban built-up areas. Studying the law of urban population density change in built-up areas is of great significance for the decision-making of national land safety and urbanization health development. Based on the data of the urban resident population and built-up areas in 285 cities in China during 2006-2016, this paper analyzes the temporal trends and spatial distribution of urban population density in Chinese cities, and explains the drivers of urban population density changes. The results show that: 1) The average population density within the built-up area in China decreased from 10 845 person/km2 in 2006 to 8 279 person/km2 in 2016, with an average annual decreasing rate of 2.66%. 2) The urban population density decreased in more than 5/6 cities, while there was a significant difference of the changing rate of population density among cities. Cities with rapidly decreased, moderately decreased, slowly decreased, and increased population density accounted for 13.3%, 30.5%, 41.1% and 15.1%, respectively. 3) Cities, experiencing rapidly decreased population density were mainly distributed in Eastern China. Cities with moderately decreased and slowly decreased population density were mainly distributed in the Central China. Cities with fast inflow of population experienced an increase of urban population density, such as Beijing, Shanghai, and Shenzhen. We also found that urban population density increased in some small cities with slow development of economy. 4) Economic development level, city scale, location factor and urban development policy are the main driving factors of population density change.

Key words: urban expansion, urban built-up area, population density, China