[Background]Climate change and intensive human activities have greatly altered the terrain landscapes,and further resulted in significant changes in hydrological processes throughout the world. In recent years,changes of the ecological environment in the upper reaches of the Yellow River have affected the life of downstream public due to natural and human factors. The objective of this study is to quantify the spatial and temporal variation of runoff and sediment load in the upper reaches of the Yellow River and their potential causes. Better understanding of the variations of runoff and sediment load is greatly helpful for soil and water conservation,water resources planning and Yellow River basin management. [Methods]This study systematically analyzed the variations of runoff and sediment load in the upper reaches of the Yellow River from 1950 to 2012 based on the observed data from 10 hydrological stations with some hydrological statistical methods. The non-parametric Mann-Kendall test and Spearman's rank correlation test were utilized to characterize the trends of hydrologic variables in the upper reaches of the Yellow River. The accumulative annual anomaly and wavelet transform method were applied to evaluate the abrupt changes and periodic characteristics of runoff and sediment load over the study period. [Results]1) Both multi-year average runoff and sediment load showed decreasing trends over the past 6 decades at 10 hydrological stations from Tangnaihai to Toudaoguai in the upper reaches of the Yellow River,and reducing trend in the most of stations was significant ( P < 0.01), while the changes at the Tangnaihai hydrological station did not display a significant trend. 2 ) The multi-year average runoff and sediment load were positively correlated,although both exhibited reduction trends. 3) The abrupt change points of annual runoff and sediment load occurred in 1968,1985,1986 and 1989, which were strongly related to the operation of large reservoirs Longyangxia and Liujiaxia. 4) The wavelet transform of monthly runoff and sediment load at 10 hydrological stations showed 0.5-1,3-5,and 7-9 years periodical fluctuation. The significant wavelet spectrum of runoff and sediment load was mainly detected before 1970s or 1990s with a period of 0.5-1 years at confidence level of 95%,but later the periodicity features became more and more insignificant and even disappeared. 5) The average annual runoff showed increasing-decreasing shift from upstream to downstream stations,while the annual sediment load had stepwise increasing trend. The average runoff and sediment load after the 1990s were lower than the multi-year average,indicating that the runoff and sediment load in the upper reaches of the Yellow River decreased significantly in recent years. [Conclusions] Both annual runoff and sediment load from Tangnaihai to Toudaoguai hydrological stations showed significantly decreasing trends. The major cause resulting in the reduction of runoff and sediment load in the upper reaches of the Yellow River were large water conservancy project,irrigation,and soil and water conservation measures on some tributaries.