Abstract：Wars happened frequently in clan society, this kind of war are called as ancient clan war or tribal war. In Dayu period, Dayu expanded his force gradually in the process of flood control and the battles or wars between tribes to make a solid foundation for passing the regime to his son. The fact that Xiaqi could take over his father' s regime successfully and found Xia dynasty shows that Dayu was the last clan chef in clan society, the creator of country and the first king of Chinese class society.

Keyword：clan war;Dayu' s flood control;public regime;the origin of civilization;