The lower reaches of the Yellow River is in the danger of changing course, as has been indicated by the annually increasing prolong and advance of its drain season and the annually increasing extension of its drain section. The impacts of this tendency have been partially shown by the tremendous economic loss and serious damage to the ecological balance. This paper makes an analysis of the causes of the drain of the Yellow River, its harmful impacts, and our inadequacy of knowledge. It also proposes some solutions to this problem for discussion.