In low water head outlet constructions,energy dissipation is a common hydraulic problem,which energy dissipation is less efficiency.The influencing factors about hydraulic characteristics and energy dissipation mechanism are very complicated,and there are no mature theories or methods to solve the problem.The thesis regards the characteristics of the low water head and large discharge per unit width of the navigation power junction on the Qingshui river as the research objects.By the hydraulic section model made in lab,the energy dissipated mechanism of the outlet constructions are discussed at first.It is proven the research results not only settle a necessary ground for the layout plan of Pingzhai navigation power junction sluice,but also be helpful for other similar projects.