Abstract: The major canal projects proposed in the national strategic planning are characterized by complex construction contents, high development intensity, affecting diverse types of ecologically sensitive areas, and both positive and negative environmental benefits. However, there are few studies on environmental impact assessment of such canal projects, especially the identification of environmental impact pathways and index systems. The matrix method and system dynamics method were used to identify the main environmental impact pathways of major canal projects. The impact assessment should focus on five aspects: water resources allocation in the basin, river hydrodynamic conditions, water environment impact, ecological environment impact and regional environmental risk. According to the analysis of environmental impact characteristics of major canal projects and combined with the requirements of environmental protection objectives, an environmental impact assessment index system of major canal projects was proposed from seven aspects, including resource utilization, hydrodynamics and water environment, ambient air, acoustic environment, ecological environment, solid waste and environmental risks, with a total of 37 assessment indexes, which could provide reference for environmental impact assessment of major canal projects and the construction of green ecological canals.