Based on observed runoff time series at the Gaojiachuan hydrologic station from 1956 through to 2012 in the Tuwei River Basin, middle reaches of the Yellow River. The recursive digital filter technique was used to separate base flow. This paper analyzed the tendency, persistence, multi-scale and mutation characteristics of hydrological series. Finally, it calculated the contribution ratio of rainfall and human activities on the base flow by SCRAQ method. Results show that: The hydrological series of base flow from 1956 to 2012 has not only significant decrease trends and persistence characteristics, but also has 22 a, 8 a multiple time-scale and mutation features. 1979 and 1996 were taken as the change points in the hydrological series of base flow. Taking 1956-1979 as the base period, the contribution rate of the precipitation and human activities to the decreased base flow was 54.16% and 45.84% in 1980-1996; and 30.11% and 69.89% in 1997-2012. The human activity driving factors increased markedly, and it can be considered under the background of global climate change, human activities have become the main influencing factors of the evolution of base flow in the Tuwei River Basin.