For the non-stationary hydrological time series, it is of great importance to explore its formation with attribution analysis to understand the hydrological process and solve the problem of water resources. Under the influence of both climate change and human activity, hydrological process in the Miyun Reservoir basin shows significantly non-stationary characteristics, while there are great differences in the results of attribution in this basin. In order to accurately reveal the causes of runoff changes in the Miyun Reservoir basin, the whole period (1960-2019) was divided into three parts: 1960-1979 for the baseline period, 1980-1998 for the change period Ⅰ, and 1999-2019 for the change period Ⅱ based on the detection result of the non-stationary characteristics of precipitation-runoff. The SWAT method, the elastic coefficient method, and the water balance method based on Budyko theory were used for attribution, and then model suitable for attribution in the Miyun Reservoir basin was selected according to the attribution results and basin characteristics. Based on the selected model, length and position of baseline period were changed to further explore the influence of baseline period on the attribution result.It was shown that attributions of elastic coefficient method and water balance method based on Budyko were similar, while the attribution of SWAT method was quite different. In the change period Ⅰ, contribution of human activities to runoff changes show as SWAT method < elastic coefficient method < water balance method. And in change period Ⅱ, results of the two methods on Budyko both showed that human activity was the main reason for the decrease of runoff, while result of SWAT showed that the impact of climate change on runoff far exceeded the impact of human activities, and became the dominant factor affecting the runoff. Cross-validation of multi-method attributions showed that the water balance method based on Budyko theory was more suitable for the attribution of runoff changes due to the construction of hydraulic projects and frequent inter-basin water transfer in the Miyun Reservoir basin. Based on the selected model, it was found that the results of attribution tended to be stable as the length of the baseline period reached 16 years. Reduction effect of human activities on runoff would be overestimated while the baseline period was shorter than 16 years. And the calculated water reduction effect of human activities was larger when the baseline period was closer to the initial position of the whole period. Considering both the effects of model and baseline period, it was concluded that human activities were the dominant factor in the runoff changes in Miyun Reservoir basin; its reduction effect on runoff fluctuated from ?128.32% to ?119.56% during the change period Ⅰ, and was about ?75.58% to ?70.70% during the change period Ⅱ. These results are helpful to improve the scientific understanding of the complex changes of the runoff and its attribution in Miyun Reservoir basin.