The one dimension mathematical model has been adopted to study the projects of the daily regulation of hydroelectric station: the implicit format of Preissmann has been adopted to solve the equation.The program of one dimension unsteady flow has been worked out.The result of calculation of the program has been verified by the result of the physical model and the coincide well.Under 4 kinds of projects of the daily regulation of Jinghong Hydroelectric Station

the unsteady flow conditions in lower reaches of the dam with the length of about 85km have been calculated by the program.The graph has been adopted to analyze the important characteristic parameters of the unstable flow conditions of 4 kinds of projects: the range of water level per day

the range of water level per hours and the range of water level per 20 minutes.Finally

the project of the daily regulation of Jinghong Hydroelectric Station which has a smallest influence on the navigable flow conditions has been obtained.