Comprehensive analysis of the characteristics, quality, and ecological effects of urban land expansion would be extremely valuable in high-quality development planning and decision-making. Using data of ten urban agglomerations of China from 1990 to 2015 at varying levels of urban development, this study analyzed the degree of urban land expansion based on the "human-land" synergistic relationship and examined the spatio-temporal characteristics and landscape ecological effects of urban development. Various development indexes for population, economy, and urban land were evaluated, including the urban land expansion intensity index, the intensity differentiation index, the landscape expansion index, and the pattern index. The results of the study are as follows: (1) From 1990 to 2015, the built-up areas in the urban agglomerations expanded continuously, while the expansion intensity showed a fluctuating trend. The highest values of expansion intensity for developed urban agglomerations appeared before 2010, while for the developing areas, the highest values came after 2010. (2) Overall, there was an asymmetrical urban growth among the agglomerations, and the areas with high urban expansion were mainly distributed along the coastal zones. At the national level, the epicenter of rapid urban growth moved from east to west, with the urban expansion in eastern China being much faster compared with the central, western, and northeastern regions. (3) The evolution in urban land use displayed two main spatial patterns, namely edge expansion and outlying, which varied based on the level of urban development. The spatial pattern in the developed urban clusters was more stable, while in the developing areas, the spatial structure started to take shape but have yet to be formed. (4) Urban expansion sprawling over suburban and rural areas resulted in relatively high degrees of fragmentation and structural complexity and instability of the landscape pattern. (5) The man-land synergy in these urban agglomerations increased gradually over time while the economy-land interaction was generally high, indicating an improvement in the overall quality of urban growth. The results of this study highlight the need to have stricter supervision of urban expansion particularly in the early stages of city development, to foster the development of small and middle-sized cities, and to propose a more balanced approach in urban land expansion. The findings here provide valuable lessons for high-quality development of land use in urban agglomerations of China.