Abstract: Proceeding from the specific property of design flood of construction period,taking ten days as time section unit,the method of moving frequency analysis is put to use on the design flood of construction period at stage of the feasibility research of Puding plant on the Sanchahe River, Guangzhao plant on the Beipanjiang River and Siting plant on the Wujiang River. On the basis of influential factors,the optimum construction plan of the 3 plants under the hydrological conditions is suggestaed.