Abstract: The flood loss share by the same river basin but different interest bodies is studied from the angle of cooperative game and global loss control. It is supposed that several agents live along the river，and if the agents choose to cooperate，the total flood loss will decrease，the space-time distribution of flood will improve，the social welfare will increase. The author discusses the base of the cooperative game，that is characteristic and distribution of core，and presents the concrete risk- share method，subgame implement method and optimum safety flow rate.

Key words: core, flood risk, cooperative game