It is importance to differentiate the effects on the change of regime in order to formulate robust water management strategies. The consistency has been destroyed in the influence of human activities and climate change. This work focuses on detecting abrupt changes in relationship of annual rainfall and runoff for the hydro meteorological stations in Wei River of the northwest China. Using double mass curve, this paper research the relationship of annual rainfall and runoff to test Wei River that have gone through decreases and abrupt changes in relationship rainfall and runoff for HX station from 1951 to 2010. In order to further verify the abrupt changes of the relationship, the Copula function was introduced into the paper. The study found that the distribution type of rainfall and runoff had changed in the variation before and after. The results show that the relationship of rainfall and runoff has undergone change in Wei Basin, and the runoff change in Wei River is significantly decreasing. Attribution analysis indicates that the primary reason of the change in relationship variation were human activities and climate change. The analysis of the variation changes of runoff would provide scientific understanding of Wei River basin and similar basins.