Abstract: The relationship between population growth and urban expansion affects the high-quality development of cities and even urban agglomerations. Trend surface and city rank-size rule was used to analysis the characteristics of evolution and allometric growth of population growth and urban area expansion from 2000 to 2018 in Yangtze River Delta. The main conclusions are as follows: (1) A high density of population and urban distribution is observed in the eastern side and the central regions, whereas the west, north and south is characterized by a low density. The pattern of population distribution has changed from equilibrium to centralization, and the pattern of land distribution has always been equilibrium. (2) The urban population-to-area allometric growth is a weak stage of population expansion with negative allometric growth. More than 70% of the cities are dominated by positive allometric growth before 2008, while more than 80% of the cities are dominated by negative allometric growth after 2008. (3)Cities in positive allometric growth is high in downward fluctuation rate, while cities in negative allometric growth is high in stability rete. It shows that the urbanization power of most cities in Yangtze River Delta is gradually transformed from land expansion to population growth.Results the research on the law of urban population area allometric growth can provide a theoretical basis for the flow of urbanization elements and the high-quality development of urban agglomerations in the Yangtze River Delta region, and provide a practical basis for the promotion of regional integration.