Abstract: To explore the relationship between the development level and connectivity of large-scale water systems, we focused on China's water resource zones as the fundamental unit. To calculate the box dimension of each primary water resource zone, the fractal theory was employed, while multiple indicators such as the tributary development coefficient ratio of tributaries were selected to comprehensively characterize the developmental level of the water systems. Besides, the graph theory was used to quantify the connectivity of water systems at the primary water resource zone level under various conditions, including watershed decomposition, optimization of large lakes, and large-scale water diversion projects. Multiple indicators, including water system loop degree, were utilized to evaluate the connectivity of the water systems. Moreover, statistical methods were employed to investigate the intrinsic relationship between indicators of water system development and connectivity. The results demonstrated that the box dimensions of China's top ten water resource zones range from 1.1 to 1.6. These zones were categorized into three levels, namely mature, relatively mature, and immature. By enhancing the graph models of each water resource zone, we could achieve a more accurate representation of the complexity and detailed characteristics of the water systems and thus could improve the precision of connectivity calculations. The correlation analysis revealed an overall positive correlation between the indicators of water system development and connectivity. Our research findings contribute to a quantitative description of the water system characteristics and connectivity in China's water resource zones, providing valuable insights into the optimization of water resource allocation and management operations.