The paper has analysed the data of check dam from typical small watershed and key trib-utaries in middle reaches of Yellow River.The conclusion has made that sediment reduction actionby check dam is obvious,and erosion redution is also notable.1.Check dam is major measures forgully control.Sediment reduction by dams approximately take 60%～70% out of the total by soiland water conservation measures;2.Silting in dams raise the erosion base.This can prevent guilybed from cutting down,and banks from expanding;3.The development potential of check dam isgreat in middle reaches of Yellow River.It is necessary further to do dam system planning reason-ably and increase input.