Abstract: The operation of public authority system should not only solve its reality, but also the rationality. In this paper, the author takes the case of the operation of public authority of water management in grass-roots communities in Shanxi Province during Ming-Qing Dynasty, proposes a comprehensive review of the rationality of public authority in the traditional village communities. The paper expands from three aspects: practical logic of public authority in the traditional rural communities, relationship between the public authority and the water rights, the provision of value identification for the public space.