Abstract: In recent years, the water flow in dry season in the middle and lower reaches of Ganjiang River has continually hit the record low, bringing greater effect on the economy and life of the cities along the river. It is necessary to study the issue about using the reservoirs in middle and upper reaches of Ganjiang River to supply water to the middle and lower reaches in dry season. On the basis of analyzing the runoff frequency，4 low flow pre-warning grades corresponding to the super drought, severe drought, moderate drought and mild drought are determined. Further, combining with the situation of urban water consumption, reservoir construction condition in the upstream, the water supply priority of users in the middle and lower reaches in dry season and the four-grade emergency response plan of water supply are put forward. The plan lays a foundation for emergency water supply to cities along the middle and lower reaches of Ganjiang River in dry season.