Abstract:The interannual variations and their trends of regional mean precipitation and r unoff at two representative hydrographical stations along the Yellow river,i.e.La nzhou and Huayuankou,during 1955-1990,and the relationship between runoff and p recipitation in different regions have been analyzed in this paper.It is found t hat the runoff anomaly has the opposite varation trend with precipitation in the upper reaches of the Yellow river,and same in the middle reaches of the Yellow river.This result indicates that precipitation anomaly is a major factor affecti ng runoff anomaly at a long time scale in the middle reaches of the Yellow river ,whereas in the upper reaches of the Yellow river,other factors such as human ag ricultural activities,snow melting associated with global warming in the source region of the Yellow river,also influence the runoff of the Yellow river.