Abstract: Due to climate change and human activities, the runoff characteristics of the upper Yangtze River have changed significantly in recent years, bringing many challenges to the development and utilization of water resources in the upper Yangtze River Basin and the functions of national strategic freshwater resource reservoirs such as the Three Gorges and the upstream reservoir group. Attribution analysis of runoff changes is of great importance to the development and utilization of water resources in the basin. Based on the observed runoff data from 1951 to 2013, statistical methods such as Mann-Kendall test, Spearman test and Pettitt test are used to diagnose the variation patterns of the Three Gorges inflow runoff. Based on the meteorological and land use data of the same period, the causes of the variation of the Three Gorges inflow runoff are further quantitatively analyzed by using the climate elasticity method, the water-energy balance equation and the SWAT. The results show that:（1） the inflow runoff of the Three Gorges was significantly changed around 1993, before 1993 the runoff was relatively natural and less affected by climate change and human activities, and after 1993 the runoff changed and was more affected.（2） During the study period, the inflow runoff from the Three Gorges decreased significantly, at a rate of 8.8 mm/10 a. Large-scale human activities in the upper Yangtze River were the main cause of the decrease in inflow runoff into the Three Gorges, while the decrease in precipitation and the increase in temperature were important causes.（3） The attribution results of the climate elasticity approach are consistent with the SWAT-based method, while the water-energy balance approach underestimates the impact of human activities on runoff.（4） SWAT takes into account the spatial and temporal changes in land use, can better describe the causes of runoff changes than the traditional “two-stage” method. These results are important to guiding the comprehensive utilization of water resources in the Three Gorges Reservoir and the rational development of water resources in the upper Yangtze River.