This paper taking Nanhai County as the center，discusses how gentries in the seaside rural world of the Pearl River Estuary in the late Qing Dynasty used the Grassroots Authority such as xiangyue 乡约，gongju 公局，and gongyue 公约 to exercise gentry power in local society under the authorization，encouragement and management of governments，so as to achieve the governance of grass roots society，thereby deepening understanding about the social governance of the seaside society.