With the development of agricultural and industrial production, and with the improvement of stand of living in the lower reach Yellow River, there is an increasing contradiction between water demand and water supply. It is essential to raise agile responding ability of water dispatching which makes sure that there is not zero-flow in the Yellow River. The mathematical foundation, implementation and software application for water dispatching of the numerical method for one-dimensional unsteady channel flow in low water evolution of lower reach as of the Yellow River are discussed in the paper. From the simulation results of low water in the 1980s, the flows fitted well, reaching to second level, which is important to dispatch water resources in Yellow River.