Water resources have characteristics of tendency and persistence. The Kendall analysis and Hurst index are applied to analyze the tendency and persistence of natural runoff in the 15 sub-regions of the Yellow River Basin during 1951-1998. The results show that the two characteristics are different in various sub-regions. For example, the annual runoff and runoff in flood-season that have passed the significance test not only have a decrease trend, but also persistence to a certain extent.