The dam site of the Qingshui River Panghai navigation and power junction project is in narrow river section of mountainous area without the working condition that ship lock and factory building are both constructing at the same time.Combining with the characteristics of large flood discharge in mountainous river,short duration of flood and high ratio of flood to dry water,we fully consider the principle of early commissioning of power generation of factory buildings,and propose the design scheme to adopt staggered diversion and overflow cofferdam.In the first stage of the design scheme，we enclose factory building of power station and part of the sluice.In the second stage,we adopt the discharge method of the overflow cofferdam and the built sluice at the same time.We establish a 1100 normal fixed bed physical model of the dam section to verify the diversion effect of the design scheme.The results show that the design indexes of scheme can meet the requirements.It can provide the conferences for the similar projects.