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Irrigation district is the basic guarantee of food security and modern agricultural development in China, as well as the important cornerstone of regional economic development and ecological environment protection. However, the unique climate, landform, and economic conditions in Northwest China make it difficult for the production capacity and ecological service function of irrigation districts to meet the needs of modern agricultural development. Based on the systematic analysis of the challenges (e.g., over-exploitation of water resources, soil salinization, agricultural water-saving, ecological environment construction, drought resistance and disaster reduction capacity, management, and maintenance) in the development of irrigation agriculture in Northwest China, the connotation and features of modern ecological irrigation district in Northwest China were put forward. According to the water source and agricultural production function, the irrigation districts in Northwest China can be divided into four types: irrigation-dependent district, irrigation-dominated district, irrigation-supplementary district, and irrigation-optimization district. Agricultural production system, material energy transmission system, and ecological environment system in irrigation district were proposed as research objects. Three core theories, namely optimal allocation theory of ecological service function, regulation theory of farmland material and energy, and ecosystem security assessment in irrigation district were proposed. Three key technologies, namely pollution control and landscape value enhancement technology, irrigation and drainage system control technology, and crop habitat integrated control technology were constructed. A theoretical and technical support system for modern ecological irrigation areas in the Northwest China was constructed, which can provide theoretical and technical guidance for the high-quality and sustainable development of irrigated agriculture in Northwest China.