Abstract: In view of the influence of various factors in the hydrological station between cascade reservoirs, it is difficult to determine the water level and flow relationship, and the use of the continuous timing method to establish the water level and flow relationship brings some inconvenience to data compilation and the application of water level and flow relationship.The equivalent area method is proposed to correct the water level change caused by the change of cross-sectional morphology, and take the Baihetan hydrological station in Jinsha River as an example, and the water level and flow relationship is established by using the data of dry and flood periods, so as to realize the single-value treatment of dry and flood periods.The results show that the method is simple and feasible, which is conducive to flow testing, data compilation and application.The water level and flow relationship is established in stages between dry and flood to provide a reference basis for the single-valued treatment of the water level and flow relationship between cascade reservoirs and hydrological stations affected by other factors.