Abstract: The construction of fishing facilities is an important measure to mitigate the adverse effects of river dams on fish.Taking the section from the dam site of Jiangjiakou to 580 m below it as the research area, a two-dimensional hydrodynamic model based on MIKE21 is constructed. According to the hydrological situation of the project, the paper analyzes the flow field of the river under typical working conditions, and explores the possible upward tracking path of fish under different conditions.The results show that: Under the condition of mainstream flow rate is 5.40~40.74 m3/s and trapped fish flow rate is 2.50 m3/s, the mainstream will flow downstream from the right bank constrained by the outflow of fish-trapping.Considering only 17.67 m3/s discharge from Unit 2,the upstream route of target fish migration is provided by simulated river course.From 30 m to 100 m away from the entrance of fish-trapping, the optimum flow velocity and water depth of fish are satisfied in the middle of the river, and fish will migrate along the middle of the river;From 0 m to 30 m, the flow velocity on the right bank increases gradually and becomes the optimum flow velocity for fish. Fish migrate from the right bank and finally reach the entrance of trapping fish.At the distance of 0 m,The water depth of the right bank is 10%~40% higher than that of the middle bank,and 90%-170% higher than that of the left bank. The high water depth at the entrance of the trapping fish will facilitate the entry of the fish.For the import confluence of “T” shaped trapping fish, the trapping fish flow accounting for about 12% can produce better hydraulic characteristics of trapping fish import.The research results can provide a reference for fish tracing at the entrance of trapping fish.