Abstract: Urban agglomerations in Yangtze River Economic Zone (YREZ) provide major contribution to urbanization in the region, and assessing the development disparity of the urban agglomerations in this area helps to understand the urbanization in this region. Using NASA’s new generation of night-time light remote sensing product (e.g. Black Marble product), this paper used night-time light growth rate, coefficient of variation (CV), Rank-Size Law and night-time light Gini Coefficient to evaluate the development disparity of the urban agglomerations in this region during 2012-2020. Comparing the urban agglomerations, Yangtze River Delta Urban Agglomeration persists the first position of size in the Yangtze River Economic Zone, and Middle Reaches of Yangtze River Urban Agglomeration has the fastest growth rate, and the Central Guizhou Urban Agglomeration develops apparently faster than the Central Yunnan Urban Agglomeration, while the overall disparity of the urban agglomerations decreased and then returned. For the disparity inside the urban agglomerations, Yangtze River Economic Zone has a clear trend of increased balance, while the trend of the other four urban agglomerations are not obvious. For the inequality among the spatial grids inside the urban agglomerations, Yangtze River Economic Zone has a decreased inequality, while Chengdu-Chongqing Urban Agglomeration, Central Guizhou Urban Agglomeration and Central Yunnan Urban Agglomeration are becoming less equal and the Yangtze River Delta Urban Agglomeration does not have clear trend. It is concluded that the core cities in the Yangtze River Delta Urban Agglomeration has obvious spillover effect, while the effect is not very significant for the other four urban agglomerations although their developments are also rapid. In sum, some possible reasons behind the development disparity of different urban agglomeration have been summarized, and transportation construction and proper development strategy which matches the advantages of the urban agglomeration can help to promote the regional coordinated development of Yangtze River Economic Zone.