Global warming and intensive changes in land use/ cover have posted unprecedented impacts on the watershed hydrology and thus the water security at the global scale. To quantitatively analyze the impacts of land use change and climate variability on the streamflow of Chaohe Watershed located in North China, we calibrated and validated a distributed hydrological model-SWAT by using the multi-site calibration procedure. The effects of land use changes and climate variability on the stream of the watershed were then explored by using scenario analysis approach. Two indices, the p-factor, r-factor as well as efficiency of objective function,were used to assess the calibration/ uncertainty performance of the SWAT model at the hydrological stations of Dage, Daiying and Xiahui within the research watershed. Results showed that p-factors in the calibration and validation periods were 0.70 and 0.77, 0.87 and 0.82, 0.92 and 0.78 respectively for the three stations. The r-factors in the calibration and validation periods were 0.63 and 0.90, 0.97 and 0.79, 0.88 and 0.92 respectively for the three stations. The objective function of efficiency of SWAT was 0.66, suggesting that the model was capable for simulating runoff responses to changes of land use and climate variability in the watershed. Compared with the baseline period (19811990), land use change caused an annual streamflow reduction of 4.1 mm whereas climate change gave rise to an annual streamflow reduction of 29.7mm in the period from 1991 to 2000. For the period of 20012009 land use change reduced runoff by 3.0 mm, whereas climate change decreased runoff for 14.3 mm. When the land use in 1999 was set as the reference, the annual streamflow would increase by 158.2% and 4.1% for the shrub land scenario and the grassland scenario, respectively. Contrarily, the farmland scenario and the woodland scenario could induce 41.7% and 23.7% annual streamflow reductions, respectively. The climate variability scenario analysis indicated that a 10% increase in annual precipitation could lead to 23.9% annual streamflow increase and a 12% increase in annual mean air temperature could lead to a 6% reduction in annual streamflow. We, therefore, concluded that the annual streamflow variation was more sensitive to precipitation than to temperature in the region. It is of critical importance to develop explicitly integrated cause-effect" land use planning and strategies for adaptive land and water management at watershed scale under the global change.