Abstract: China’s economy has shifted from high-speed growth to high-quality development, and the shared development has become the fundamental objective. Based on the evaluation index system of prefectural units and shared development, this study quantitatively evaluates the differences and changes in shared development levels in the Yangtze River Economic Belt from 2010 to 2020. The results show that: the shared development levels of different scale grade cities decreased in order. The downstream area forms a high agglomeration area with Shanghai, Nanjing, and Hangzhou as the core, with strong radiation-driven effects. In the upstream and midstream areas, Wuhan and Chengdu form two extreme value centers, but with weak radiation-driven effects. From 2010 to 2020, the first class of central cities is steadily increasing in general, the second class of central cities and regional central cities are significantly elevated, while the regional central cities differ between uplift and subsidence, and other cities are lowering significantly. The Yangtze River Delta region and part of the midstream areas are significantly growing, and other cities of the upstream and midstream areas are significant decreasing. The gap between downstream and upstream is widening. The difference in cultural resources is the most obvious factor, followed by the fiscal expenditure on social security and employment. The economically developed areas enjoy a high level of shared development in compulsory education, culture, social security, and employment, while the economically backward areas have the advantages in health and medical community and environmental greening. The results show the advantages and disadvantages of the sharing development level of different scale-grade cities, and provide a basis for the formulation of differentiated policies for the high-quality development of the Yangtze River Economic Belt.