The evolution characteristics of dried up days of river play an important role in recognizing the regional hydrological processes and clarifying the influencing mechanism of human activities, such as hydraulic engineering and water allocation in various fields. Based on the hydrological and climatic data from 1951 to 2014, this study uses Mann-Kendall methods and statistic models of precipitation and runoff accumulation curve to analyze the temporal evolution of dried up days and the influencing mechanisms at the Three Outlets of southern Jingjiang in the middle reach of Yangtze River. The results are as follows: 1) The average dried up days at the Three Outlets increased during 1951-2014 and the trend was significant. The average dried up days also increased during the period of 2003-2014, but the trend was not obvious, namely, the increase trend of the dried up days slowed down. 2) The variation of dried up days was controlled by the variation of runoff at the Three Outlets. And the runoff variations could be explained by climate fluctuations, such as precipitation and evapotranspiration, and human activities, such as hydraulic engineering and water allocation. Which one is the main control remains uncertain. So it is important to separate the influence factors. 3) Using the previous period as the reference period, the contributions of climate fluctuation to the increment of dried up days in each period were 24.93%, 19.05%, 6.36%, 10.38% and 7.56% during the five periods (1959-1966, 1967-1972, 1972-1980, 1981-2002 and 2003-2014), respectively, whereas the contributions of human activity were 75.07%, 80.75%, 93.64%, 89.62% and 92.44% respectively. The result revealed that the increment of dried up days was mainly dominated by human activities from 1951 to 2014.