Analysisof the ecological base fow is the basis to solve the problem of ecological environment deterioration in the Dawenhe RiverBasin. Acording to the annual runoffdata from the Dawenkou Station, the Tennant method and basic flow ratio method were used to calculate theecological base flow.And the amount of the ecological base flow in the Dawenhe River were determined by calculating the base flow for fishspawning breeding in the dferent level years, and taking the water structures and ecological base flow loss into consideration. The results showthat the base flow of 1.1~14.1m'/s is better for the ecological water demand with the ecological base flow security degree reaching more than 90%.