Aiming at the problems existing in the construction of ecological fishway in Qianwei Navigation-Hydropower Junction，such as great disturbance in channel slope excavation，difficulty in ensuring the compactness，difficulty in connecting the anti-seepage geomembrane of the channel，irregular changes in the route of ecological fishway，and tedious work in slope excavation survey and setting-out，the construction technology of ecological fishway was studied. Firstly，the feasibility of the design scheme of imitating ecological fishway in Qianwei Navigation and Hydropower Junction was verified by fishway model test and fish ecology test. Then，combined with the characteristics of imitating ecological fishway，the fishway channel shape，fishway flexible seepage control and fishway slope rolling were studied to ensure the fishway construction quality and fishway structure stability. This paper analyzes the flow pattern of fishway pond chamber and the maximum flow velocity of fish passing control section，puts forward the influence of fishway curve and diaphragm permeability on flow velocity，and reasonably sets up the rest pond to ensure the target fish to pass through fishway smoothly. Using local natural building materials，the natural migration channel of fish is constructed，which conforms to the ecological principle and meets the requirements of ecological protection.