In this paper, the characteristics of annual runoff data of Wudinghe river in the year of 1956-2000 are the sensitive degree of influence from climate factors in the drainage area are analyzed. Based on the datum before abrupt change of annual runoff, the plural linear regression model for annual runoff is set up. The difference between the value derived by the function and the true value is the influence resulted by human activity. The analysis shows that the annual runoff of Wudinghe river decreased evidently, and the runoff changed abruptly in 1971. The influence resulted by human activity is increasing year by year. And in the year of 1997, human influence on river runoff reached maximum, with its value being 56.9%. So the conclusion is reached that in the climate background of global warming the driving force of the change in annual runoff is human activity.