Hydrological analysis requires the time-series consistency of runoff data,but the changing environment ruins the stability of runoff series. Under the influence of climate change and frequent human activities(water conservancy project construction, change of vegetation cover,and urbanization construction), the underlying surface conditions and physical mechanism of runoff yield have undergone obvious changes,resulting in runoff series variation, which can not meet the consistency requirement and identical distribution assumption of hydrological time series. In this paper, we identified the trend components, mutation components, cyclical components, and random components of the annual and monthly runoff and rainfall time sequences recorded at the Xiahui Station in the lower reaches of Chao River during 1976-2012 by using non-parametric Mann-Kendall rank test,Pettitt test, and variance analysis. By comparing these components between runoff and rainfall time sequences,this paper concludes that the rainfall is not the only one factor that leads to runoff changes,and that climate change and human activities both influence the evolution process of the lower reaches of Chao River basin.