Abstract <p>The Yangtze River Basin, as China's largest river system, plays a crucial role in regional socio-economic development and ecological security. However, rapid urbanization and intensive human activities have exerted immense pressure on its water environment, leading to complex spatiotemporal changes in water quality. This study revealed the spatial and temporal differentiation characteristics of multiple water quality indicators in the Yangtze River Basin and their influencing factors based on Kriging interpolation analysis and principal component analysis. It was found that their spatial and temporal variations of dissolved oxygen (DO), pH, electrical conductivity (EC), turbidity (TB), permanganate index (COD_Mn), ammonia nitrogen (NH₃-N), total nitrogen (TN), and total phosphorus (TP) may have relationship with regional environmental characteristics and water body types to some extent. Principal component analysis identified three dominant factors. PC1 may characterize the degree of water environmental pollution, PC2 may reflect the comprehensive water quality stress index of the Yangtze River Basin, and PC3 may reflect the acid–base buffering effect of surface water in the Yangtze River Basin and its control over the water chemical balance. Along the main stem direction, spatial patterns emerged: pH values first decreased and then increased, while COD_Mn showed a continuous increase, indicating the significant influence of local environments on water quality evolution. Notably, NH₃-N in lake systems was grouped into the PC3 principal component, revealing that its migration and transformation mechanisms may differ from those in the main stem and tributary systems. These findings provide a scientific basis for differentiated water environmental management in the Yangtze River Basin, offering significant guidance value, particularly in coordinating economic development with aquatic ecological protection.</p>