Abstract: Research was conducted in a tributary of the Yellow River, Wei River. Streamflow at Huaxian station during the period of 1958 -2011 were applied to identify the trends and abrupt changes by using Mann-Kendall test, non-parametric Pettitt test and double mass curve analysis in the Wei River basin.The simple water balance model was employed to quantify the effects of climate variability and human activities on streamflow. Results show that 1) a remarkable decrease trend in annual streamflow were detected with the rate of 0.86 mm/ a. 2) an abrupt change was identified in 1994. The streamflow time series were then divided into two periods, i. e., the baseline period (1958 - 1994) and the changed period (1995 - 2011). 3) Streamflow during the changed period decreased by 64.6%, 41.3% and 45.5% in dry year, normal year and wet year, respectively. 4) In the controlled region of Huaxian station, it was found that precipitation variability and human activities accounted for about 49.0% and 51.0% of the change in streamflow. Additionally, the effect of climate change on streamflow was mostlycaused by precipitation decrease in the Wei River basin.